Measurement of J=ψ and ψð2SÞ Prompt Double-Differential Cross Sections in pp Collisions at ffiffi s p ¼ 7 TeV V. Khachatryan et al. * (CMS Collaboration) (Received 13 February 2015; published 14 May 2015) The double-differential cross sections of promptly produced J=ψ and ψð2SÞmesons are measured in pp collisions at ffiffiffi s p ¼ 7 TeV, as a function of transverse momentum pT and absolute rapidity jyj. The analysis uses J=ψ and ψð2SÞ dimuon samples collected by the CMS experiment, corresponding to integrated luminosities of 4.55 and 4.90 fb−1, respectively. The results are based on a two-dimensional analysis of the dimuon invariant mass and decay length, and extend to pT ¼ 120 and 100 GeV for the J=ψ and ψð2SÞ, respectively, when integrated over the interval jyj < 1.2. The ratio of the ψð2SÞ to J=ψ cross sections is also reported for jyj < 1.2, over the range 10 < pT < 100 GeV. These are the highest pT values for which the cross sections and ratio have been measured. DOI: 10.1103/PhysRevLett.114.191802 PACS numbers: 13.20.Gd, 13.85.Qk, 13.88.+e Studies of heavy-quarkonium production are of central importance for an improved understanding of non- perturbative quantum chromodynamics (QCD) [1]. The nonrelativistic QCD (NRQCD) effective-field-theory framework [2], arguably the best formalism at this time, factorizes high-pT quarkonium production in short-distance and long-distance scales. First, a heavy quark-antiquark pair, QQ̄, is produced in a Fock state 2Sþ1L½a� J , with spin S, orbital angularmomentumL, and total angularmomentum J that are either identical to (color singlet, a ¼ 1) or different from (color octet, a ¼ 8) those of the corresponding quarkonium state. The QQ̄ cross sections are determined by short-distance coefficients (SDCs), kinematic-dependent functions calculable perturbatively as expansions in the strong-coupling constant αs. Then this “preresonant” QQ̄ pair binds into the physically observable quarkonium through a nonperturbative evolution that may change L and S, with bound-state formation probabilities proportional to long-distance matrix elements (LDMEs). The LDMEs are conjectured to be constant (i.e., independent of the QQ̄ momentum) and universal (i.e., process independent). The color-octet terms are expected to scale with powers of the heavy-quark velocity in the QQ̄ rest frame. In the nonrelativistic limit, an S-wave vector quarkonium state should be formed from a QQ̄ pair produced as a color singlet (3S½1�1 ) or as one of three color octets (1S½8�0 , 3S½8�1 , and 3P½8� J ). Three “global fits” to measured quarkonium data [3–5] obtained incompatible octet LDMEs, despite the use of essentially identical theory inputs: next-to-leading-order (NLO) QCD calculations of the singlet and octet SDCs. The disagreement stems from the fact that different sets of measurements were considered. In particular, the results crucially depend on the minimum pT of the fitted measure- ments [6], because the octet SDCs have differentpT depend- ences. Fits including low-pT cross sections lead to the conclusion that, at high pT , quarkonium production should be dominated by transversely polarized octet terms. This prediction is in stark contradiction with the unpolarized production seen by the CDF [7,8] and CMS [9,10] experi- ments, an observation known as the “quarkonium polariza- tion puzzle.” As shown in Ref. [6], the puzzle is seemingly solved by restricting the NRQCD global fits to high-pT quarkonia, indicating that the presently available fixed-order calculations provide SDCs that are unable to reproduce reality at lower pT values or that NRQCD factorization only holds for pT values much larger than the quarkonium mass. The polarization measurements add a crucial dimension to the global fits because the various channels have remarkably distinct polarization properties: in the helicity frame, 3S½1�1 is longitudinally polarized, 1S½8�0 is unpolarized, 3S½8�1 is trans- versely polarized, and 3P½8� J has a polarization that changes significantly with pT . Bottomonium and prompt charmo- nium polarizations reaching or exceeding pT ¼ 50 GeV were measured by CMS [9,10], using a very robust analysis framework [11,12], on thebasis of event samples collected in 2011. Instead, the differential charmonium cross sections published by CMS [13] are based on data collected in 2010 and have a much lower pT reach. Measurements of prompt charmonium cross sections extending well beyond pT ¼ 50 GeVwill trigger improvedNRQCDglobal fits, restricted to a kinematic domain where the factorization formalism is *Full author list given at the end of the article. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distri- bution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 0031-9007=15=114(19)=191802(16) 191802-1 © 2015 CERN, for the CMS Collaboration http://dx.doi.org/10.1103/PhysRevLett.114.191802 http://dx.doi.org/10.1103/PhysRevLett.114.191802 http://dx.doi.org/10.1103/PhysRevLett.114.191802 http://dx.doi.org/10.1103/PhysRevLett.114.191802 http://creativecommons.org/licenses/by/3.0/ http://creativecommons.org/licenses/by/3.0/ unquestioned, and will provide more accurate and reli- able LDMEs. This Letter presents measurements of the double- differential cross sections ofJ=ψ andψð2SÞmesonspromptly produced inpp collisions at a center-of-mass energyof7TeV, based on dimuon event samples collected by CMS in 2011. They complement other prompt charmonium cross sections measured at the LHC, by ATLAS [14,15], LHCb [16,17], and ALICE [18]. The analysis is made in four bins of absolute rapidity (jyj < 0.3, 0.3 < jyj < 0.6, 0.6 < jyj < 0.9, and 0.9 < jyj < 1.2) and in the pT ranges 10–95 GeV for the J=ψ and 10–75 GeV for the ψð2SÞ. A rapidity-integrated result in the range jyj < 1.2 is also pro- vided, extending the pT reach to 120 GeV for the J=ψ and 100 GeV for the ψð2SÞ. The corresponding ψð2SÞ over J=ψ cross section ratios are also reported. The dimuon invariant massdistribution isused toseparate theJ=ψ andψð2SÞ signals from other processes, mostly pairs of uncorrelated muons, while the dimuon decay length is used to separate the non- promptcharmonia,comingfromdecaysofbhadrons,fromthe prompt component. Feed-down from decays of heavier charmonium states, approximately 33% of the prompt J=ψ cross section [19], is not distinguished from the directly produced charmonia. The CMS apparatus is based on a superconducting solenoid of 6 m internal diameter, providing a 3.8 T field. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorim- eter, and a brass and scintillator hadron calorimeter. Muons are measured with three kinds of gas-ionization detectors: drift tubes, cathode strip chambers, and resistive-plate chambers. The main subdetectors used in this analysis are the silicon tracker and the muon system, which enable the measurement of muon momenta over the pseudora- pidity range jηj < 2.4. A more detailed description of the CMS detector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref. [20]. The events were collected using a two-level trigger system. The first level, made of custom hardware process- ors, uses data from the muon system to select events with two muon candidates. The high-level trigger, adding information from the silicon tracker, reduces the rate of stored events by requiring an opposite-sign muon pair of invariant mass 2.8 < M < 3.35 GeV, pT > 9.9 GeV, and jyj < 1.25 for the J=ψ trigger, and 3.35 < M < 4.05 GeV and pT > 6.9 GeV for the ψð2SÞ trigger. No pT require- ment is imposed on the single muons at trigger level. Both triggers require a dimuon vertex fit χ2 probability greater than 0.5% and a distance of closest approach between the two muons less than 5 mm. Events where the muons bend towards each other in the magnetic field are rejected to lower the trigger rate while retaining the highest-quality dimuons. The J=ψ and ψð2SÞ analyses are conducted independently, using event samples separated at the trigger level. The ψð2SÞ sample corresponds to an integrated luminosity of 4.90 fb−1, while the J=ψ sample has a reduced value, 4.55 fb−1, because the pT threshold of the J=ψ trigger was raised to 12.9 GeV in a fraction of the data-taking period; the integrated luminosities have an uncertainty of 2.2% [21]. The muon tracks are required to have hits in at least eleven tracker layers, with at least two in the silicon pixel detector, and to be matched with at least one segment in the muon system. They must have a good track fit quality (χ2 per degree of freedom smaller than 1.8) and point to the interaction region. The selected muons must also match in pseudorapidity and azimuthal angle with the muon objects responsible for triggering the event. The analysis is restricted to muons produced within a fiducial phase-space window where the muon detection efficiencies are accurately measured: pT > 4.5, 3.5, and 3.0 GeV for the regions jηj < 1.2, 1.2 < jηj < 1.4, and 1.4 < jηj < 1.6, respectively. The combinatorial dimuon background is reduced by requiring a dimuon vertex fit χ2 probability larger than 1%. After applying the event selection criteria, the combined yields of prompt and nonprompt charmonia in the range jyj < 1.2 are 5.45 M for the J=ψ and 266 k for the ψð2SÞ. The prompt charmonia are separated from those resulting from decays of b hadrons through the use of the dimuon pseudo-proper-decay-length [22], l ¼ LxyM=pT , where Lxy is the transverse decay length in the laboratory frame, measured after removing the two muon tracks from the calculation of the primary vertex position. For events with multiple collision vertices, Lxy is calculated with respect to the vertex closest to the direction of the dimuon momentum, extrapolated towards the beam line. For each ðjyj; pTÞ bin, the prompt charmonium yields are evaluated through an extended unbinned maximum- likelihood fit to the two-dimensional ðM;lÞ event distri- bution. In the mass dimension, the shape of each signal peak is represented by a Crystal Ball (CB) function [23], with free mean (μCB) and width (σCB) parameters. Given the strong correlation between the two CB tail parameters, αCB and nCB, they are fixed to values evaluated from fits to event samples integrated in broader pT ranges. A single CB function provides a good description of the signal mass peaks, given that the dimuon mass distributions are studied in narrow ðjyj; pTÞ bins, within which the dimuon invariant mass resolution has a negligible variation. The mass distribution of the underlying continuum background is described by an exponential function. Concerning the pseudo-proper-decay-length variable, the prompt signal component is modeled by a resolution function, which exploits the per-event uncertainty information provided by the vertex reconstruction algorithm, while the nonprompt charmonium term is modeled by an exponential function convolved with the resolution function. The continuum background component is represented by a sum of prompt PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-2 and nonprompt empirical forms. The distributions are well described with a relatively small number of free parameters. Figure 1 shows the J=ψ and ψð2SÞ dimuon invariant mass and pseudo-proper-decay-length projections for two representative ðjyj; pTÞ bins. The decay length projections are shown for events with dimuon invariant mass within �3σCB of the pole mass. In the highest pT bins, where the number of dimuons is relatively small, stable results are obtained by fixing μCB and the slope of the exponential-like function describing the nonprompt combinatorial back- ground to values extrapolated from the trend found from the lower-pT bins. The systematic uncertainties in the signal yields are evaluated by repeating the fit with different functional forms, varying the values of the fixed param- eters, and allowing for more free parameters in the fit. The fit results are robust with respect to changes in the procedure; the corresponding systematic uncertainties are negligible at low pT and increase to ≈2% for the J=ψ and ≈6% for the ψð2SÞ in the highest pT bins. The single-muon detection efficiencies ϵμ are measured with a “tag-and-probe” (T&P) technique [24], using event samples collected with triggers specifically designed for this purpose, including a sample enriched in dimuons from J=ψ decays where a muon is combined with another track and the pair is required to have an invariant mass within the range 2.8–3.4 GeV. The procedure was validated in the phase-space window of the analysis with detailed Monte Carlo (MC) simulation studies. The measured efficiencies are parametrized as a function of muon pT , in eight bins of muon jηj. Their uncertainties, reflecting the statistical precision of the T&P samples and possible imperfections of the parametrization, are ≈2%–3%. The efficiency of the dimuon vertex fit χ2 probability require- ment is also measured with the T&P approach, using a sample of events collected with a dedicated (prescaled) trigger. It is around 95%–97%, improving with increasing pT , with a 2% systematic uncertainty. At high pT , when the two muons might be emitted relatively close to each other, the efficiency of the dimuon trigger ϵμμ is smaller than the product of the two single-muon efficiencies [13], ϵμμ ¼ ϵμ1ϵμ2ρ. The correction factor ρ is evaluated with MC simulations, validated from data collected with single- muon triggers. For pT < 35 GeV, ρ is consistent with being unity, within a systematic uncertainty estimated as 2.85 2.9 2.95 3 3.05 3.1 3.15 3.2 3.25 3.3 E ve nt s / 4 M eV 0 50 100 150 200 250 300 350 400 450 Data Total Prompt Nonprompt Background CMS ψJ/ < 32 GeV T 30 < p (7 TeV)-14.55 fb Dimuon invariant mass [GeV] Pseudo-proper decay length [mm] -0.5 0 0.5 1 1.5 2 2.5 mμ E ve nt s / 2 0 -110 1 10 210 310 Data Total Prompt Nonprompt Background CMS ψJ/ < 32 GeV T 30 < p (7 TeV)-14.55 fb Dimuon invariant mass [GeV] 3.4 3.5 3.6 3.7 3.8 3.9 4 E ve nt s / 1 4 M eV 0 50 100 150 200 250 300 350 Data Total Prompt Nonprompt Background CMS (2S)ψ < 27.5 GeV T 25 < p (7 TeV)-14.9 fb Pseudo-proper decay length [mm] -0.5 0 0.5 1 1.5 2 2.5 mμ E ve nt s / 2 0 -110 1 10 210 Data Total Prompt Nonprompt Background CMS (2S)ψ < 27.5 GeV T 25 < p (7 TeV)-14.9 fb FIG. 1 (color online). Projections on the dimuon invariant mass (left) and pseudo-proper-decay-length (right) axes, for the J=ψ (top) and ψð2SÞ (bottom) events in the kinematic bins given in the plots. The right panels show dimuons of invariant mass within�3σCB of the pole masses. The curves, identified in the legends, represent the result of the fits described in the text. The vertical bars on the data points show the statistical uncertainties. PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-3 2%, except in the 0.9 < jyj < 1.2 bin, where the uncer- tainty increases to 4.3% for the J=ψ if pT < 12 GeV, and to 2.7% for the ψð2SÞ if pT < 11 GeV. For pT > 35 GeV, ρ decreases approximately linearly with pT , reaching 60%–70% for pT ∼ 85 GeV, with systematic uncertainties evaluated by comparing the MC simulation results with estimations made using data collected with single-muon triggers: 5% up to pT ¼ 50 (55) GeV for the J=ψ [ψð2SÞ] and 10% for higher pT. The total dimuon detection efficiency increases from ϵμμ ≈ 78% at pT ¼ 15 GeV to ≈85% at 30 GeV, and then decreases to ≈65% at 80 GeV. To obtain the charmonium cross sections in each ðjyj; pTÞ bin without any restrictions on the kinematic variables of the two muons, we correct for the corresponding dimuon acceptance, defined as the fraction of dimuon decays having both muons emitted within the single-muon fiducial phase space. These acceptances are calculated using a detailedMC simulation of the CMS experiment. Charmonia are generated using a flat rapidity distribution andpT distributions basedon previousmeasurements [13]; using flatpT distributions leads to negligible changes. The particles are decayed by EVTGEN [25] interfaced to PYTHIA 6.4 [26], while PHOTOS [27] is used to simulate final-state radiation. The fractions of J=ψ and ψð2SÞ dimuon events in a given ðjyj; pTÞ bin with both muons surviving the fiducial selections depend on the decay kinematics and, in particular, on the polarization of the mother particle. Acceptances are calculated using polariza- tion scenarios corresponding to different values of the polar anisotropy parameter in the helicity frame, λHX ϑ : 0 (unpolar- ized), þ1 (transverse), and −1 (longitudinal). A fourth scenario, corresponding to λHX ϑ ¼ þ0.10 for the J=ψ and þ0.03 for the ψð2SÞ, reflects the results published by CMS [10]. The two other parameters characterizing the dimuon angular distributions [28], λφ and λϑφ, have beenmeasured to be essentially zero [10] andhave a negligible influence on the acceptance. The acceptances are essentially identical for the two charmonia and are almost rapidity independent for jyj < 1.2. The two-dimensional acceptance maps are calcu- lated with large MC simulation samples, so that statistical fluctuations are small, and in narrow jyj bins, so that variations within the bins can be neglected. Since the efficiencies and acceptances are evaluated for events where the two muons bend away from each other, a factor of 2 is applied to obtain the final cross sections. The double-differential cross sections of promptly pro- duced J=ψ and ψð2SÞ in the dimuon channel, Bd2σ=dpTdy, where B is the J=ψ or ψð2SÞ dimuon branching fraction, are obtained by dividing the fitted prompt-signal yields, already corrected on an event-by- event basis for efficiencies and acceptance, by the inte- grated luminosity and the widths of the pT and jyj bins. The numerical values, including the relative statistical and systematic uncertainties, are reported for both charmonia, five rapidity intervals, and four polarization scenarios in Tables 1–4 of the Supplemental Material [29]. Figure 2 shows the results obtained in the unpolarized scenario. With respect to the jyj < 0.3 bin, the cross sections drop by ≈5% for 0.6 < jyj < 0.9 and ≈15% for 0.9 < jyj < 1.2. Measuring the charmonium production cross sections in the broader rapidity range jyj < 1.2 has the advantage that the increased statistical accuracy allows the measurement to be extended to higher-pT values, where comparisons with theoretical calculations are particularly informative. Figure 3 compares the rapidity-integrated (unpolarized) cross sections, after rescaling with the branching fraction B of the dimuon decay channels [30], with results reported by ATLAS [14,15]. The curve represents a fit of the J=ψ cross section measured in this analysis to a power-law function [31]. The band labeled FKLSW represents the result of a global fit [6] comparing SDCs calculated at NLO [3] with ψð2SÞ cross sections and polarizations previously reported by CMS [10,13] and LHCb [17]. According to that fit, ψð2SÞmesons are produced predominantly unpolarized. At high pT , the values reported in this Letter tend to be higher than the band, which is essentially determined from results for pT < 30 GeV. The ratio of the ψð2SÞ to J=ψ differential cross sections is also measured in the jyj < 1.2 range, recomputing the J=ψ values in the pT bins of the ψð2SÞ analysis. The measured values are reported in Table 5 of the Supplemental Material [29]. The corrections owing to the integrated luminosity, acceptances, and efficiencies cancel to a large extent in the measurement of the ratio. The total systematic uncertainty, dominated by the ρ correction for pT > 30 GeV and by the acceptance and [GeV] T p 0 20 40 60 80 100 120 [ n b / G eV ] y d T p / d σ d -610 -510 -410 -310 -210 -110 1 CMS -1 2)×y y < 1.2 ( < 0.3 y y y < 0.60.3 < < 0.90.6 < < 1.20.9 < of 2.2% not included Luminosity uncertainty ψJ/ (2S)ψ ψ : L = 4.55 fbJ/ (2S) : L = 4.90 fbψ -1 = 7 TeVspp 2 FIG. 2 (color online). The J=ψ and ψð2SÞ differential pT cross sections times the dimuon branching fractions for four rapidity bins and integrated over the range jyj < 1.2 (scaled up by a factor of 2 for presentation purposes), assuming the unpolarized scenario. The vertical bars show the statistical and systematic uncertainties added in quadrature. PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-4 efficiency corrections for pT < 20 GeV, does not exceed 3%, except for pT > 75 GeV, where it reaches 5%. Larger event samples are needed to clarify the trend of the ratio for pT above ≈35 GeV. In summary, the double-differential cross sections of the J=ψ and ψð2SÞmesons promptly produced in pp collisions at ffiffiffi s p ¼ 7 TeV have been measured as a function of pT in four jyj bins, as well as integrated over the jyj < 1.2 range, extending up to or beyond pT ¼ 100 GeV. New global fits of cross sections and polarizations, including these high-pT measurements, will probe the theoretical calculations in a kinematical region where NRQCD factorization is believed to be most reliable. The new data should also provide input to stringent tests of recent theory developments, such as those described in Refs. [32–34]. We congratulate our colleagues in the CERN accelerator departments for the excellent performance of the LHC and thank the technical and administrative staffs at CERN and at other CMS institutes for their contributions to the success of the CMS effort. In addition, we gratefully acknowledge the computing centers and personnel of the Worldwide LHC Computing Grid for delivering so effectively the computing infrastructure essential to our analyses. Finally, we acknowledge the enduring support for the construction and operation of the LHC and the CMS detector provided by the following funding agencies: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); MoER, ERC IUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/ IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (USA). 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Paktinat Mehdiabadi,53 F. Rezaei Hosseinabadi,53 B. Safarzadeh,53,z M. Zeinali,53 M. Felcini,54 M. Grunewald,54 M. Abbrescia,55a,55b C. Calabria,55a,55b S. S. Chhibra,55a,55b A. Colaleo,55a D. Creanza,55a,55c L. Cristella,55a,55b N. De Filippis,55a,55c M. De Palma,55a,55b L. Fiore,55a G. Iaselli,55a,55c G. Maggi,55a,55c M. Maggi,55a S. My,55a,55c S. Nuzzo,55a,55b A. Pompili,55a,55b G. Pugliese,55a,55c R. Radogna,55a,55b,c G. Selvaggi,55a,55b A. Sharma,55a L. Silvestris,55a,c R. Venditti,55a,55b P. Verwilligen,55a G. Abbiendi,56a A. C. Benvenuti,56a D. Bonacorsi,56a,56b S. Braibant-Giacomelli,56a,56b L. Brigliadori,56a,56b R. Campanini,56a,56b P. Capiluppi,56a,56b A. Castro,56a,56b F. R. Cavallo,56a G. Codispoti,56a,56b M. Cuffiani,56a,56b G. M. Dallavalle,56a F. Fabbri,56a A. Fanfani,56a,56b D. Fasanella,56a,56b P. Giacomelli,56a C. Grandi,56a L. Guiducci,56a,56b S. Marcellini,56a G. Masetti,56a A. Montanari,56a F. L. Navarria,56a,56b A. Perrotta,56a A. M. Rossi,56a,56b T. Rovelli,56a,56b G. P. Siroli,56a,56b N. Tosi,56a,56b R. Travaglini,56a,56b S. Albergo,57a,57b G. Cappello,57a M. Chiorboli,57a,57b S. Costa,57a,57b F. Giordano,57a,c R. Potenza,57a,57b A. Tricomi,57a,57b C. Tuve,57a,57b G. Barbagli,58a V. Ciulli,58a,58b C. Civinini,58a R. D’Alessandro,58a,58b E. Focardi,58a,58b E. Gallo,58a S. Gonzi,58a,58b V. Gori,58a,58b P. Lenzi,58a,58b M. Meschini,58a S. Paoletti,58a G. Sguazzoni,58a A. Tropiano,58a,58b L. Benussi,59 S. Bianco,59 F. Fabbri,59 D. Piccolo,59 R. Ferretti,60a,60b F. Ferro,60a M. Lo Vetere,60a,60b E. Robutti,60a S. Tosi,60a,60b M. E. Dinardo,61a,61b S. Fiorendi,61a,61b S. Gennai,61a,c R. Gerosa,61a,61b,c A. Ghezzi,61a,61b P. Govoni,61a,61b M. T. Lucchini,61a,61b,c S. Malvezzi,61a R. A. Manzoni,61a,61b A. Martelli,61a,61b B. Marzocchi,61a,61b,c D. Menasce,61a L. Moroni,61a M. Paganoni,61a,61b D. Pedrini,61a S. Ragazzi,61a,61b N. Redaelli,61a T. Tabarelli de Fatis,61a,61b S. Buontempo,62a N. Cavallo,62a,62c S. Di Guida,62a,62d,c F. Fabozzi,62a,62c A. O. M. Iorio,62a,62b L. Lista,62a S. Meola,62a,62d,c M. Merola,62a P. Paolucci,62a,c P. Azzi,63a N. Bacchetta,63a D. Bisello,63a,63b R. Carlin,63a,63b P. Checchia,63a M. Dall’Osso,63a,63b T. Dorigo,63a U. Dosselli,63a F. Gasparini,63a,63b U. Gasparini,63a,63b A. Gozzelino,63a S. Lacaprara,63a M. Margoni,63a,63b A. T. Meneguzzo,63a,63b F. Montecassiano,63a M. Passaseo,63a J. Pazzini,63a,63b N. Pozzobon,63a,63b P. Ronchese,63a,63b F. Simonetto,63a,63b E. Torassa,63a M. Tosi,63a,63b P. Zotto,63a,63b A. Zucchetta,63a,63b G. Zumerle,63a,63b M. Gabusi,64a,64b S. P. Ratti,64a,64b V. Re,64a C. Riccardi,64a,64b P. Salvini,64a P. Vitulo,64a,64b M. Biasini,65a,65b G. M. Bilei,65a D. Ciangottini,65a,65b,c L. Fanò,65a,65b P. Lariccia,65a,65b G. Mantovani,65a,65b M. Menichelli,65a A. Saha,65a A. Santocchia,65a,65b A. Spiezia,65a,65b,c K. Androsov,66a,aa P. Azzurri,66a G. Bagliesi,66a J. Bernardini,66a T. Boccali,66a G. Broccolo,66a,66c R. Castaldi,66a M. A. Ciocci,66a,aa R. Dell’Orso,66a S. Donato,66a,66c,c G. Fedi,66a F. Fiori,66a,66c L. Foà,66a,66c A. Giassi,66a M. T. Grippo,66a,aa F. Ligabue,66a,66c T. Lomtadze,66a L. Martini,66a,66b A. Messineo,66a,66b C. S. Moon,66a,bb F. Palla,66a,c A. Rizzi,66a,66b A. Savoy-Navarro,66a,cc A. T. Serban,66a P. Spagnolo,66a P. Squillacioti,66a,aa R. Tenchini,66a G. Tonelli,66a,66b A. Venturi,66a P. G. Verdini,66a C. Vernieri,66a,66c L. Barone,67a,67b F. Cavallari,67a G. D’imperio,67a,67b D. Del Re,67a,67b M. Diemoz,67a C. Jorda,67a E. Longo,67a,67b F. Margaroli,67a,67b P. Meridiani,67a F. Micheli,67a,67b,c G. Organtini,67a,67b R. Paramatti,67a S. Rahatlou,67a,67b C. Rovelli,67a F. Santanastasio,67a,67b L. Soffi,67a,67b P. Traczyk,67a,67b,c N. Amapane,68a,68b R. Arcidiacono,68a,68c S. Argiro,68a,68b M. Arneodo,68a,68c R. Bellan,68a,68b C. Biino,68a N. Cartiglia,68a S. Casasso,68a,68b,c M. Costa,68a,68b R. Covarelli,68a PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-8 A. Degano,68a,68b N. Demaria,68a L. Finco,68a,68b,c C. Mariotti,68a S. Maselli,68a E. Migliore,68a,68b V. Monaco,68a,68b M. Musich,68a M. M. Obertino,68a,68c L. Pacher,68a,68b N. Pastrone,68a M. Pelliccioni,68a G. L. Pinna Angioni,68a,68b A. Potenza,68a,68b A. Romero,68a,68b M. Ruspa,68a,68c R. Sacchi,68a,68b A. Solano,68a,68b A. Staiano,68a U. Tamponi,68a S. Belforte,69a V. Candelise,69a,69b,c M. Casarsa,69a F. Cossutti,69a G. Della Ricca,69a,69b B. Gobbo,69a C. La Licata,69a,69b M. Marone,69a,69b A. Schizzi,69a,69b T. Umer,69a,69b A. Zanetti,69a S. Chang,70 A. Kropivnitskaya,70 S. K. Nam,70 D. H. Kim,71 G. N. Kim,71 M. S. Kim,71 D. J. Kong,71 S. Lee,71 Y. D. Oh,71 H. Park,71 A. Sakharov,71 D. C. Son,71 T. J. Kim,72 M. S. Ryu,72 J. Y. Kim,73 D. H. Moon,73 S. Song,73 S. Choi,74 D. Gyun,74 B. Hong,74 M. Jo,74 H. Kim,74 Y. Kim,74 B. Lee,74 K. S. Lee,74 S. K. Park,74 Y. Roh,74 H. D. Yoo,75 M. Choi,76 J. H. Kim,76 I. C. Park,76 G. Ryu,76 Y. Choi,77 Y. K. Choi,77 J. Goh,77 D. Kim,77 E. Kwon,77 J. Lee,77 I. Yu,77 A. Juodagalvis,78 J. R. Komaragiri,79 M. A. B. Md Ali,79,dd W. A. T. Wan Abdullah,79 E. Casimiro Linares,80 H. Castilla-Valdez,80 E. De La Cruz-Burelo,80 I. Heredia-de La Cruz,80 A. Hernandez-Almada,80 R. Lopez-Fernandez,80 A. Sanchez-Hernandez,80 S. Carrillo Moreno,81 F. Vazquez Valencia,81 I. Pedraza,82 H. A. Salazar Ibarguen,82 A. Morelos Pineda,83 D. Krofcheck,84 P. H. Butler,85 S. Reucroft,85 A. Ahmad,86 M. Ahmad,86 Q. Hassan,86 H. R. Hoorani,86 W. A. Khan,86 T. Khurshid,86 M. Shoaib,86 H. Bialkowska,87 M. Bluj,87 B. Boimska,87 T. Frueboes,87 M. Górski,87 M. Kazana,87 K. Nawrocki,87 K. Romanowska-Rybinska,87 M. Szleper,87 P. Zalewski,87 G. Brona,88 K. Bunkowski,88 M. Cwiok,88 W. Dominik,88 K. Doroba,88 A. Kalinowski,88 M. Konecki,88 J. Krolikowski,88 M. Misiura,88 M. Olszewski,88 P. Bargassa,89 C. Beirão Da Cruz E Silva,89 P. Faccioli,89 P. G. Ferreira Parracho,89 M. Gallinaro,89 L. Lloret Iglesias,89 F. Nguyen,89 J. Rodrigues Antunes,89 J. Seixas,89 D. Vadruccio,89 J. Varela,89 P. Vischia,89 S. Afanasiev,90 I. Golutvin,90 V. Karjavin,90 V. Konoplyanikov,90 V. Korenkov,90 G. Kozlov,90 A. Lanev,90 A. Malakhov,90 V. Matveev,90,ee V. V. Mitsyn,90 P. Moisenz,90 V. Palichik,90 V. Perelygin,90 S. Shmatov,90 N. Skatchkov,90 V. Smirnov,90 E. Tikhonenko,90 A. Zarubin,90 V. Golovtsov,91 Y. Ivanov,91 V. Kim,91,ff E. Kuznetsova,91 P. Levchenko,91 V. Murzin,91 V. Oreshkin,91 I. Smirnov,91 V. Sulimov,91 L. Uvarov,91 S. Vavilov,91 A. Vorobyev,91 An. Vorobyev,91 Yu. Andreev,92 A. Dermenev,92 S. Gninenko,92 N. Golubev,92 M. Kirsanov,92 N. Krasnikov,92 A. Pashenkov,92 D. Tlisov,92 A. Toropin,92 V. Epshteyn,93 V. Gavrilov,93 N. Lychkovskaya,93 V. Popov,93 I. Pozdnyakov,93 G. Safronov,93 S. Semenov,93 A. Spiridonov,93 V. Stolin,93 E. Vlasov,93 A. Zhokin,93 V. Andreev,94 M. Azarkin,94 I. Dremin,94 M. Kirakosyan,94 A. Leonidov,94 G. Mesyats,94 S. V. Rusakov,94 A. Vinogradov,94 A. Belyaev,95 E. Boos,95 M. Dubinin,95,gg L. Dudko,95 A. Ershov,95 A. Gribushin,95 V. Klyukhin,95 O. Kodolova,95 I. Lokhtin,95 S. Obraztsov,95 S. Petrushanko,95 V. Savrin,95 A. Snigirev,95 I. Azhgirey,96 I. Bayshev,96 S. Bitioukov,96 V. Kachanov,96 A. Kalinin,96 D. Konstantinov,96 V. Krychkine,96 V. Petrov,96 R. Ryutin,96 A. Sobol,96 L. Tourtchanovitch,96 S. Troshin,96 N. Tyurin,96 A. Uzunian,96 A. Volkov,96 P. Adzic,97,hh M. Ekmedzic,97 J. Milosevic,97 V. Rekovic,97 J. Alcaraz Maestre,98 C. Battilana,98 E. Calvo,98 M. Cerrada,98 M. Chamizo Llatas,98 N. Colino,98 B. De La Cruz,98 A. Delgado Peris,98 D. Domínguez Vázquez,98 A. Escalante Del Valle,98 C. Fernandez Bedoya,98 J. P. Fernández Ramos,98 J. Flix,98 M. C. Fouz,98 P. Garcia-Abia,98 O. Gonzalez Lopez,98 S. Goy Lopez,98 J. M. Hernandez,98 M. I. Josa,98 E. Navarro De Martino,98 A. Pérez-Calero Yzquierdo,98 J. Puerta Pelayo,98 A. Quintario Olmeda,98 I. Redondo,98 L. Romero,98 M. S. Soares,98 C. Albajar,99 J. F. de Trocóniz,99 M. Missiroli,99 D. Moran,99 H. Brun,100 J. Cuevas,100 J. Fernandez Menendez,100 S. Folgueras,100 I. Gonzalez Caballero,100 J. A. Brochero Cifuentes,101 I. J. Cabrillo,101 A. Calderon,101 J. Duarte Campderros,101 M. Fernandez,101 G. Gomez,101 A. Graziano,101 A. Lopez Virto,101 J. Marco,101 R. Marco,101 C. Martinez Rivero,101 F. Matorras,101 F. J. Munoz Sanchez,101 J. Piedra Gomez,101 T. Rodrigo,101 A. Y. Rodríguez-Marrero,101 A. Ruiz-Jimeno,101 L. Scodellaro,101 I. Vila,101 R. Vilar Cortabitarte,101 D. Abbaneo,102 E. Auffray,102 G. Auzinger,102 M. Bachtis,102 P. Baillon,102 A. H. Ball,102 D. Barney,102 A. Benaglia,102 J. Bendavid,102 L. Benhabib,102 J. F. Benitez,102 P. Bloch,102 A. Bocci,102 A. Bonato,102 O. Bondu,102 C. Botta,102 H. Breuker,102 T. Camporesi,102 G. Cerminara,102 S. Colafranceschi,102,ii M. D’Alfonso,102 D. d’Enterria,102 A. Dabrowski,102 A. David,102 F. De Guio,102 A. De Roeck,102 S. De Visscher,102 E. Di Marco,102 M. Dobson,102 M. Dordevic,102 B. Dorney,102 N. Dupont-Sagorin,102 A. Elliott-Peisert,102 G. Franzoni,102 W. Funk,102 D. Gigi,102 K. Gill,102 D. Giordano,102 M. Girone,102 F. Glege,102 R. Guida,102 S. Gundacker,102 M. Guthoff,102 J. Hammer,102 M. Hansen,102 P. Harris,102 J. Hegeman,102 V. Innocente,102 P. Janot,102 K. Kousouris,102 K. Krajczar,102 P. Lecoq,102 C. Lourenço,102 N. Magini,102 L. Malgeri,102 M. Mannelli,102 J. Marrouche,102 L. Masetti,102 F. Meijers,102 S. Mersi,102 E. Meschi,102 F. Moortgat,102 S. Morovic,102 M. Mulders,102 S. Orfanelli,102 L. Orsini,102 L. Pape,102 E. Perez,102 A. Petrilli,102 G. Petrucciani,102 A. Pfeiffer,102 M. Pimiä,102 D. Piparo,102 M. Plagge,102 A. Racz,102 G. Rolandi,102,jj M. Rovere,102 H. Sakulin,102 C. Schäfer,102 C. Schwick,102 A. Sharma,102 P. Siegrist,102 P. Silva,102 M. Simon,102 P. Sphicas,102,kk D. Spiga,102 J. Steggemann,102 PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-9 B. Stieger,102 M. Stoye,102 Y. Takahashi,102 D. Treille,102 A. Tsirou,102 G. I. Veres,102,s N. Wardle,102 H. K. Wöhri,102 H. Wollny,102 W. D. Zeuner,102 W. Bertl,103 K. Deiters,103 W. Erdmann,103 R. Horisberger,103 Q. Ingram,103 H. C. Kaestli,103 D. Kotlinski,103 U. Langenegger,103 D. Renker,103 T. Rohe,103 F. Bachmair,104 L. Bäni,104 L. Bianchini,104 M. A. Buchmann,104 B. Casal,104 N. Chanon,104 G. Dissertori,104 M. Dittmar,104 M. Donegà,104 M. Dünser,104 P. Eller,104 C. Grab,104 D. Hits,104 J. Hoss,104 G. Kasieczka,104 W. Lustermann,104 B. Mangano,104 A. C. Marini,104 M. Marionneau,104 P. Martinez Ruiz del Arbol,104 M. Masciovecchio,104 D. Meister,104 N. Mohr,104 P. Musella,104 C. Nägeli,104,ll F. Nessi-Tedaldi,104 F. Pandolfi,104 F. Pauss,104 L. Perrozzi,104 M. Peruzzi,104 M. Quittnat,104 L. Rebane,104 M. Rossini,104 A. Starodumov,104,mm M. Takahashi,104 K. Theofilatos,104 R. Wallny,104 H. A. Weber,104 C. Amsler,105,nn M. F. Canelli,105 V. Chiochia,105 A. De Cosa,105 A. Hinzmann,105 T. Hreus,105 B. Kilminster,105 C. Lange,105 J. Ngadiuba,105 D. Pinna,105 P. Robmann,105 F. J. Ronga,105 S. Taroni,105 Y. Yang,105 M. Cardaci,106 K. H. Chen,106 C. Ferro,106 C. M. Kuo,106 W. Lin,106 Y. J. Lu,106 R. Volpe,106 S. S. Yu,106 P. Chang,107 Y. H. Chang,107 Y. Chao,107 K. F. Chen,107 P. H. Chen,107 C. Dietz,107 U. Grundler,107 W.-S. Hou,107 Y. F. Liu,107 R.-S. Lu,107 M. Miñano Moya,107 E. Petrakou,107 J. F. Tsai,107 Y. M. Tzeng,107 R. Wilken,107 B. Asavapibhop,108 G. Singh,108 N. Srimanobhas,108 N. Suwonjandee,108 A. Adiguzel,109 M. N. Bakirci,109,oo S. Cerci,109,pp C. Dozen,109 I. Dumanoglu,109 E. Eskut,109 S. Girgis,109 G. Gokbulut,109 Y. Guler,109 E. Gurpinar,109 I. Hos,109 E. E. Kangal,109,qq A. Kayis Topaksu,109 G. Onengut,109,rr K. Ozdemir,109,ss S. Ozturk,109,oo A. Polatoz,109 D. Sunar Cerci,109,pp B. Tali,109,pp H. Topakli,109,oo M. Vergili,109 C. Zorbilmez,109 I. V. Akin,110 B. Bilin,110 S. Bilmis,110 H. Gamsizkan,110,tt B. Isildak,110,uu G. Karapinar,110,vv K. Ocalan,110,ww S. Sekmen,110 U. E. Surat,110 M. Yalvac,110 M. Zeyrek,110 E. A. Albayrak,111,xx E. Gülmez,111 M. Kaya,111,yy O. Kaya,111,zz T. Yetkin,111,aaa K. Cankocak,112 F. I. Vardarlı,112 L. Levchuk,113 P. Sorokin,113 J. J. Brooke,114 E. Clement,114 D. Cussans,114 H. Flacher,114 J. Goldstein,114 M. Grimes,114 G. P. Heath,114 H. F. Heath,114 J. Jacob,114 L. Kreczko,114 C. Lucas,114 Z. Meng,114 D. M. Newbold,114,bbb S. Paramesvaran,114 A. Poll,114 T. Sakuma,114 S. Seif El Nasr-storey,114 S. Senkin,114 V. J. Smith,114 K.W. Bell,115 A. Belyaev,115,ccc C. Brew,115 R. M. Brown,115 D. J. A. Cockerill,115 J. A. Coughlan,115 K. Harder,115 S. Harper,115 E. Olaiya,115 D. Petyt,115 C. H. Shepherd-Themistocleous,115 A. Thea,115 I. R. Tomalin,115 T. Williams,115 W. J. Womersley,115 S. D. Worm,115 M. Baber,116 R. Bainbridge,116 O. Buchmuller,116 D. Burton,116 D. Colling,116 N. Cripps,116 P. Dauncey,116 G. Davies,116 M. Della Negra,116 P. Dunne,116 A. Elwood,116 W. Ferguson,116 J. Fulcher,116 D. Futyan,116 G. Hall,116 G. Iles,116 M. Jarvis,116 G. Karapostoli,116 M. Kenzie,116 R. Lane,116 R. Lucas,116,bbb L. Lyons,116 A.-M. Magnan,116 S. Malik,116 B. Mathias,116 J. Nash,116 A. Nikitenko,116,mm J. Pela,116 M. Pesaresi,116 K. Petridis,116 D. M. Raymond,116 S. Rogerson,116 A. Rose,116 C. Seez,116 P. Sharp,116,a A. Tapper,116 M. Vazquez Acosta,116 T. Virdee,116 S. C. Zenz,116 J. E. Cole,117 P. R. Hobson,117 A. Khan,117 P. Kyberd,117 D. Leggat,117 D. Leslie,117 I. D. Reid,117 P. Symonds,117 L. Teodorescu,117 M. Turner,117 J. Dittmann,118 K. Hatakeyama,118 A. Kasmi,118 H. Liu,118 N. Pastika,118 T. Scarborough,118 Z. Wu,118 O. Charaf,119 S. I. Cooper,119 C. Henderson,119 P. Rumerio,119 A. Avetisyan,120 T. Bose,120 C. Fantasia,120 P. Lawson,120 C. Richardson,120 J. Rohlf,120 J. St. John,120 L. Sulak,120 J. Alimena,121 E. Berry,121 S. Bhattacharya,121 G. Christopher,121 D. Cutts,121 Z. Demiragli,121 N. Dhingra,121 A. Ferapontov,121 A. Garabedian,121 U. Heintz,121 E. Laird,121 G. Landsberg,121 Z. Mao,121 M. Narain,121 S. Sagir,121 T. Sinthuprasith,121 T. Speer,121 J. Swanson,121 R. Breedon,122 G. Breto,122 M. Calderon De La Barca Sanchez,122 S. Chauhan,122 M. Chertok,122 J. Conway,122 R. Conway,122 P. T. Cox,122 R. Erbacher,122 M. Gardner,122 W. Ko,122 R. Lander,122 M. Mulhearn,122 D. Pellett,122 J. Pilot,122 F. Ricci-Tam,122 S. Shalhout,122 J. Smith,122 M. Squires,122 D. Stolp,122 M. Tripathi,122 S. Wilbur,122 R. Yohay,122 R. Cousins,123 P. Everaerts,123 C. Farrell,123 J. Hauser,123 M. Ignatenko,123 G. Rakness,123 E. Takasugi,123 V. Valuev,123 M. Weber,123 K. Burt,124 R. Clare,124 J. Ellison,124 J. W. Gary,124 G. Hanson,124 J. Heilman,124 M. Ivova Rikova,124 P. Jandir,124 E. Kennedy,124 F. Lacroix,124 O. R. Long,124 A. Luthra,124 M. Malberti,124 M. Olmedo Negrete,124 A. Shrinivas,124 S. Sumowidagdo,124 S. Wimpenny,124 J. G. Branson,125 G. B. Cerati,125 S. Cittolin,125 R. T. D’Agnolo,125 A. Holzner,125 R. Kelley,125 D. Klein,125 J. Letts,125 I. Macneill,125 D. Olivito,125 S. Padhi,125 C. Palmer,125 M. Pieri,125 M. Sani,125 V. Sharma,125 S. Simon,125 M. Tadel,125 Y. Tu,125 A. Vartak,125 C. Welke,125 F. Würthwein,125 A. Yagil,125 G. Zevi Della Porta,125 D. Barge,126 J. Bradmiller-Feld,126 C. Campagnari,126 T. Danielson,126 A. Dishaw,126 V. Dutta,126 K. Flowers,126 M. Franco Sevilla,126 P. Geffert,126 C. George,126 F. Golf,126 L. Gouskos,126 J. Incandela,126 C. Justus,126 N. Mccoll,126 S. D. Mullin,126 J. Richman,126 D. Stuart,126 W. To,126 C. West,126 J. Yoo,126 A. Apresyan,127 A. Bornheim,127 J. Bunn,127 Y. Chen,127 J. Duarte,127 A. Mott,127 H. B. Newman,127 C. Pena,127 M. Pierini,127 M. Spiropulu,127 J. R. Vlimant,127 R. Wilkinson,127 S. Xie,127 R. Y. Zhu,127 V. Azzolini,128 A. Calamba,128 B. Carlson,128 T. Ferguson,128 Y. Iiyama,128 M. Paulini,128 J. Russ,128 H. Vogel,128 I. Vorobiev,128 J. P. Cumalat,129 PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-10 W. T. Ford,129 A. Gaz,129 M. Krohn,129 E. Luiggi Lopez,129 U. Nauenberg,129 J. G. Smith,129 K. Stenson,129 S. R. Wagner,129 J. Alexander,130 A. Chatterjee,130 J. Chaves,130 J. Chu,130 S. Dittmer,130 N. Eggert,130 N. Mirman,130 G. Nicolas Kaufman,130 J. R. Patterson,130 A. Ryd,130 E. Salvati,130 L. Skinnari,130 W. Sun,130 W. D. Teo,130 J. Thom,130 J. Thompson,130 J. Tucker,130 Y. Weng,130 L. Winstrom,130 P. Wittich,130 D. Winn,131 S. Abdullin,132 M. Albrow,132 J. Anderson,132 G. Apollinari,132 L. A. T. Bauerdick,132 A. Beretvas,132 J. Berryhill,132 P. C. Bhat,132 G. Bolla,132 K. Burkett,132 J. N. Butler,132 H.W. K. Cheung,132 F. Chlebana,132 S. Cihangir,132 V. D. Elvira,132 I. Fisk,132 J. Freeman,132 E. Gottschalk,132 L. Gray,132 D. Green,132 S. Grünendahl,132 O. Gutsche,132 J. Hanlon,132 D. Hare,132 R. M. Harris,132 J. Hirschauer,132 B. Hooberman,132 S. Jindariani,132 M. Johnson,132 U. Joshi,132 B. Klima,132 B. Kreis,132 S. Kwan,132,a J. Linacre,132 D. Lincoln,132 R. Lipton,132 T. Liu,132 R. Lopes De Sá,132 J. Lykken,132 K. Maeshima,132 J. M. Marraffino,132 V. I. Martinez Outschoorn,132 S. Maruyama,132 D. Mason,132 P. McBride,132 P. Merkel,132 K. Mishra,132 S. Mrenna,132 S. Nahn,132 C. Newman-Holmes,132 V. O’Dell,132 O. Prokofyev,132 E. Sexton-Kennedy,132 A. Soha,132 W. J. Spalding,132 L. Spiegel,132 L. Taylor,132 S. Tkaczyk,132 N. V. Tran,132 L. Uplegger,132 E.W. Vaandering,132 R. Vidal,132 A. Whitbeck,132 J. Whitmore,132 F. Yang,132 D. Acosta,133 P. Avery,133 P. Bortignon,133 D. Bourilkov,133 M. Carver,133 D. Curry,133 S. Das,133 M. De Gruttola,133 G. P. Di Giovanni,133 R. D. Field,133 M. Fisher,133 I. K. Furic,133 J. Hugon,133 J. Konigsberg,133 A. Korytov,133 T. Kypreos,133 J. F. Low,133 K. Matchev,133 H. Mei,133 P. Milenovic,133,ddd G. Mitselmakher,133 L. Muniz,133 A. Rinkevicius,133 L. Shchutska,133 M. Snowball,133 D. Sperka,133 J. Yelton,133 M. Zakaria,133 S. Hewamanage,134 S. Linn,134 P. Markowitz,134 G. Martinez,134 J. L. Rodriguez,134 J. R. Adams,135 T. Adams,135 A. Askew,135 J. Bochenek,135 B. Diamond,135 J. Haas,135 S. Hagopian,135 V. Hagopian,135 K. F. Johnson,135 H. Prosper,135 V. Veeraraghavan,135 M. Weinberg,135 M.M. Baarmand,136 M. Hohlmann,136 H. Kalakhety,136 F. Yumiceva,136 M. R. Adams,137 L. Apanasevich,137 D. Berry,137 R. R. Betts,137 I. Bucinskaite,137 R. Cavanaugh,137 O. Evdokimov,137 L. Gauthier,137 C. E. Gerber,137 D. J. Hofman,137 P. Kurt,137 C. O’Brien,137 I. D. Sandoval Gonzalez,137 C. Silkworth,137 P. Turner,137 N. Varelas,137 B. Bilki,138,eee W. Clarida,138 K. Dilsiz,138 M. Haytmyradov,138 V. Khristenko,138 J.-P. Merlo,138 H. Mermerkaya,138,fff A. Mestvirishvili,138 A. Moeller,138 J. Nachtman,138 H. Ogul,138 Y. Onel,138 F. Ozok,138,xx A. Penzo,138 R. Rahmat,138 S. Sen,138 P. Tan,138 E. Tiras,138 J. Wetzel,138 K. Yi,138 I. Anderson,139 B. A. Barnett,139 B. Blumenfeld,139 S. Bolognesi,139 D. Fehling,139 A. V. Gritsan,139 P. Maksimovic,139 C. Martin,139 M. Swartz,139 M. Xiao,139 P. Baringer,140 A. Bean,140 G. Benelli,140 C. Bruner,140 J. Gray,140 R. P. Kenny III,140 D. Majumder,140 M. Malek,140 M. Murray,140 D. Noonan,140 S. Sanders,140 J. Sekaric,140 R. Stringer,140 Q. Wang,140 J. S. Wood,140 I. Chakaberia,141 A. Ivanov,141 K. Kaadze,141 S. Khalil,141 M. Makouski,141 Y. Maravin,141 L. K. Saini,141 N. Skhirtladze,141 I. Svintradze,141 J. Gronberg,142 D. Lange,142 F. Rebassoo,142 D. Wright,142 C. Anelli,143 A. Baden,143 A. Belloni,143 B. Calvert,143 S. C. Eno,143 J. A. Gomez,143 N. J. Hadley,143 S. Jabeen,143 R. G. Kellogg,143 T. Kolberg,143 Y. Lu,143 A. C. Mignerey,143 K. Pedro,143 Y. H. Shin,143 A. Skuja,143 M. B. Tonjes,143 S. C. Tonwar,143 A. Apyan,144 R. Barbieri,144 K. Bierwagen,144 W. Busza,144 I. A. Cali,144 L. Di Matteo,144 G. Gomez Ceballos,144 M. Goncharov,144 D. Gulhan,144 M. Klute,144 Y. S. Lai,144 Y.-J. Lee,144 A. Levin,144 P. D. Luckey,144 C. Paus,144 D. Ralph,144 C. Roland,144 G. Roland,144 G. S. F. Stephans,144 K. Sumorok,144 D. Velicanu,144 J. Veverka,144 B. Wyslouch,144 M. Yang,144 M. Zanetti,144 V. Zhukova,144 B. Dahmes,145 A. Gude,145 S. C. Kao,145 K. Klapoetke,145 Y. Kubota,145 J. Mans,145 S. Nourbakhsh,145 R. Rusack,145 A. Singovsky,145 N. Tambe,145 J. Turkewitz,145 J. G. Acosta,146 S. Oliveros,146 E. Avdeeva,147 K. Bloom,147 S. Bose,147 D. R. Claes,147 A. Dominguez,147 R. Gonzalez Suarez,147 J. Keller,147 D. Knowlton,147 I. Kravchenko,147 J. Lazo-Flores,147 F. Meier,147 F. Ratnikov,147 G. R. Snow,147 M. Zvada,147 J. Dolen,148 A. Godshalk,148 I. Iashvili,148 A. Kharchilava,148 A. Kumar,148 S. Rappoccio,148 G. Alverson,149 E. Barberis,149 D. Baumgartel,149 M. Chasco,149 A. Massironi,149 D. M. Morse,149 D. Nash,149 T. Orimoto,149 D. Trocino,149 R.-J. Wang,149 D. Wood,149 J. Zhang,149 K. A. Hahn,150 A. Kubik,150 N. Mucia,150 N. Odell,150 B. Pollack,150 A. Pozdnyakov,150 M. Schmitt,150 S. Stoynev,150 K. Sung,150 M. Trovato,150 M. Velasco,150 S. Won,150 A. Brinkerhoff,151 K. M. Chan,151 A. Drozdetskiy,151 M. Hildreth,151 C. Jessop,151 D. J. Karmgard,151 N. Kellams,151 K. Lannon,151 S. Lynch,151 N. Marinelli,151 Y. Musienko,151,ee T. Pearson,151 M. Planer,151 R. Ruchti,151 G. Smith,151 N. Valls,151 M. Wayne,151 M. Wolf,151 A. Woodard,151 L. Antonelli,152 J. Brinson,152 B. Bylsma,152 L. S. Durkin,152 S. Flowers,152 A. Hart,152 C. Hill,152 R. Hughes,152 K. Kotov,152 T. Y. Ling,152 W. Luo,152 D. Puigh,152 M. Rodenburg,152 B. L. Winer,152 H. Wolfe,152 H.W. Wulsin,152 O. Driga,153 P. Elmer,153 J. Hardenbrook,153 P. Hebda,153 S. A. Koay,153 P. Lujan,153 D. Marlow,153 T. Medvedeva,153 M. Mooney,153 J. Olsen,153 P. Piroué,153 X. Quan,153 H. Saka,153 D. Stickland,153,c C. Tully,153 J. S. Werner,153 A. Zuranski,153 E. Brownson,154 S. Malik,154 H. Mendez,154 J. E. Ramirez Vargas,154 V. E. Barnes,155 D. Benedetti,155 D. Bortoletto,155 L. Gutay,155 Z. Hu,155 M. K. Jha,155 M. Jones,155 K. Jung,155 M. Kress,155 N. Leonardo,155 PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-11 D. H. Miller,155 N. Neumeister,155 F. Primavera,155 B. C. Radburn-Smith,155 X. Shi,155 I. Shipsey,155 D. Silvers,155 A. Svyatkovskiy,155 F. Wang,155 W. Xie,155 L. Xu,155 J. Zablocki,155 N. Parashar,156 J. Stupak,156 A. Adair,157 B. Akgun,157 K. M. Ecklund,157 F. J. M. Geurts,157 W. Li,157 B. Michlin,157 B. P. Padley,157 R. Redjimi,157 J. Roberts,157 J. Zabel,157 B. Betchart,158 A. Bodek,158 P. de Barbaro,158 R. Demina,158 Y. Eshaq,158 T. Ferbel,158 M. Galanti,158 A. Garcia-Bellido,158 P. Goldenzweig,158 J. Han,158 A. Harel,158 O. Hindrichs,158 A. Khukhunaishvili,158 S. Korjenevski,158 G. Petrillo,158 M. Verzetti,158 D. Vishnevskiy,158 R. Ciesielski,159 L. Demortier,159 K. Goulianos,159 C. Mesropian,159 S. Arora,160 A. Barker,160 J. P. Chou,160 C. Contreras-Campana,160 E. Contreras-Campana,160 D. Duggan,160 D. Ferencek,160 Y. Gershtein,160 R. Gray,160 E. Halkiadakis,160 D. Hidas,160 E. Hughes,160 S. Kaplan,160 A. Lath,160 S. Panwalkar,160 M. Park,160 S. Salur,160 S. Schnetzer,160 D. Sheffield,160 S. Somalwar,160 R. Stone,160 S. Thomas,160 P. Thomassen,160 M. Walker,160 K. Rose,161 S. Spanier,161 A. York,161 O. Bouhali,162,ggg A. Castaneda Hernandez,162 M. Dalchenko,162 M. De Mattia,162 S. Dildick,162 R. Eusebi,162 W. Flanagan,162 J. Gilmore,162 T. Kamon,162,hhh V. Khotilovich,162 V. Krutelyov,162 R. Montalvo,162 I. Osipenkov,162 Y. Pakhotin,162 R. Patel,162 A. Perloff,162 J. Roe,162 A. Rose,162 A. Safonov,162 I. Suarez,162 A. Tatarinov,162 K. A. Ulmer,162 N. Akchurin,163 C. Cowden,163 J. Damgov,163 C. Dragoiu,163 P. R. Dudero,163 J. Faulkner,163 K. Kovitanggoon,163 S. Kunori,163 S.W. Lee,163 T. Libeiro,163 I. Volobouev,163 E. Appelt,164 A. G. Delannoy,164 S. Greene,164 A. Gurrola,164 W. Johns,164 C. Maguire,164 Y. Mao,164 A. Melo,164 M. Sharma,164 P. Sheldon,164 B. Snook,164 S. Tuo,164 J. Velkovska,164 M.W. Arenton,165 S. Boutle,165 B. Cox,165 B. Francis,165 J. Goodell,165 R. Hirosky,165 A. Ledovskoy,165 H. Li,165 C. Lin,165 C. Neu,165 E. Wolfe,165 J. Wood,165 C. Clarke,166 R. Harr,166 P. E. Karchin,166 C. Kottachchi Kankanamge Don,166 P. Lamichhane,166 J. Sturdy,166 D. A. Belknap,167 D. Carlsmith,167 M. Cepeda,167 S. Dasu,167 L. Dodd,167 S. Duric,167 E. Friis,167 R. Hall-Wilton,167 M. Herndon,167 A. Hervé,167 P. Klabbers,167 A. Lanaro,167 C. Lazaridis,167 A. Levine,167 R. Loveless,167 A. Mohapatra,167 I. Ojalvo,167 T. Perry,167 G. A. Pierro,167 G. Polese,167 I. Ross,167 T. Sarangi,167 A. Savin,167 W. H. Smith,167 D. Taylor,167 C. Vuosalo167 and N. Woods167 (CMS Collaboration) 1Yerevan Physics Institute, Yerevan, Armenia 2Institut für Hochenergiephysik der OeAW, Wien, Austria 3National Centre for Particle and High Energy Physics, Minsk, Belarus 4Universiteit Antwerpen, Antwerpen, Belgium 5Vrije Universiteit Brussel, Brussel, Belgium 6Université Libre de Bruxelles, Bruxelles, Belgium 7Ghent University, Ghent, Belgium 8Université Catholique de Louvain, Louvain-la-Neuve, Belgium 9Université de Mons, Mons, Belgium 10Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil 11Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil 12aUniversidade Estadual Paulista, São Paulo, Brazil 12bUniversidade Federal do ABC, São Paulo, Brazil 13Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria 14University of Sofia, Sofia, Bulgaria 15Institute of High Energy Physics, Beijing, China 16State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China 17Universidad de Los Andes, Bogota, Colombia 18University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split, Croatia 19University of Split, Faculty of Science, Split, Croatia 20Institute Rudjer Boskovic, Zagreb, Croatia 21University of Cyprus, Nicosia, Cyprus 22Charles University, Prague, Czech Republic 23Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt 24National Institute of Chemical Physics and Biophysics, Tallinn, Estonia 25Department of Physics, University of Helsinki, Helsinki, Finland 26Helsinki Institute of Physics, Helsinki, Finland 27Lappeenranta University of Technology, Lappeenranta, Finland 28DSM/IRFU, CEA/Saclay, Gif-sur-Yvette, France PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-12 29Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France 30Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France 31Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France 32Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Villeurbanne, France 33Institute of High Energy Physics and Informatization, Tbilisi State University, Tbilisi, Georgia 34RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany 35RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany 36RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany 37Deutsches Elektronen-Synchrotron, Hamburg, Germany 38University of Hamburg, Hamburg, Germany 39Institut für Experimentelle Kernphysik, Karlsruhe, Germany 40Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece 41University of Athens, Athens, Greece 42University of Ioánnina, Ioánnina, Greece 43Wigner Research Centre for Physics, Budapest, Hungary 44Institute of Nuclear Research ATOMKI, Debrecen, Hungary 45University of Debrecen, Debrecen, Hungary 46National Institute of Science Education and Research, Bhubaneswar, India 47Panjab University, Chandigarh, India 48University of Delhi, Delhi, India 49Saha Institute of Nuclear Physics, Kolkata, India 50Bhabha Atomic Research Centre, Mumbai, India 51Tata Institute of Fundamental Research, Mumbai, India 52Indian Institute of Science Education and Research (IISER), Pune, India 53Institute for Research in Fundamental Sciences (IPM), Tehran, Iran 54University College Dublin, Dublin, Ireland 55aINFN Sezione di Bari, Bari, Italy 55bUniversità di Bari, Bari, Italy 55cPolitecnico di Bari, Bari, Italy 56aINFN Sezione di Bologna, Bologna, Italy 56bUniversità di Bologna, Bologna, Italy 57aINFN Sezione di Catania, Catania, Italy 57bUniversità di Catania, Catania, Italy 57cCSFNSM, Catania, Italy 58aINFN Sezione di Firenze, Firenze, Italy 58bUniversità di Firenze, Firenze, Italy 59INFN Laboratori Nazionali di Frascati, Frascati, Italy 60aINFN Sezione di Genova, Genova, Italy 60bUniversità di Genova, Genova, Italy 61aINFN Sezione di Milano-Bicocca, Milano, Italy 61bUniversità di Milano-Bicocca, Milano, Italy 62aINFN Sezione di Napoli, Napoli, Italy 62bUniversità di Napoli ’Federico II’, Napoli, Italy 62cUniversità della Basilicata (Potenza), Napoli, Italy 62dUniversità G. Marconi (Roma), Napoli, Italy 63aINFN Sezione di Padova, Padova, Italy 63bUniversità di Padova, Padova, Italy 63cUniversità di Trento (Trento), Padova, Italy 64aINFN Sezione di Pavia, Pavia, Italy 64bUniversità di Pavia, Pavia, Italy 65aINFN Sezione di Perugia, Perugia, Italy 65bUniversità di Perugia, Perugia, Italy 66aINFN Sezione di Pisa, Pisa, Italy 66bUniversità di Pisa, Pisa, Italy 66cScuola Normale Superiore di Pisa, Pisa, Italy 67aINFN Sezione di Roma, Roma, Italy 67bUniversità di Roma, Roma, Italy 68aINFN Sezione di Torino, Torino, Italy 68bUniversità di Torino, Torino, Italy PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-13 68cUniversità del Piemonte Orientale (Novara), Torino, Italy 69aINFN Sezione di Trieste, Trieste, Italy 69bUniversità di Trieste, Trieste, Italy 70Kangwon National University, Chunchon, Korea 71Kyungpook National University, Daegu, Korea 72Chonbuk National University, Jeonju, Korea 73Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Korea 74Korea University, Seoul, Korea 75Seoul National University, Seoul, Korea 76University of Seoul, Seoul, Korea 77Sungkyunkwan University, Suwon, Korea 78Vilnius University, Vilnius, Lithuania 79National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia 80Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico 81Universidad Iberoamericana, Mexico City, Mexico 82Benemerita Universidad Autonoma de Puebla, Puebla, Mexico 83Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico 84University of Auckland, Auckland, New Zealand 85University of Canterbury, Christchurch, New Zealand 86National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan 87National Centre for Nuclear Research, Swierk, Poland 88Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland 89Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal 90Joint Institute for Nuclear Research, Dubna, Russia 91Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia 92Institute for Nuclear Research, Moscow, Russia 93Institute for Theoretical and Experimental Physics, Moscow, Russia 94P.N. Lebedev Physical Institute, Moscow, Russia 95Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia 96State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia 97University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia 98Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain 99Universidad Autónoma de Madrid, Madrid, Spain 100Universidad de Oviedo, Oviedo, Spain 101Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain 102CERN, European Organization for Nuclear Research, Geneva, Switzerland 103Paul Scherrer Institut, Villigen, Switzerland 104Institute for Particle Physics, ETH Zurich, Zurich, Switzerland 105Universität Zürich, Zurich, Switzerland 106National Central University, Chung-Li, Taiwan 107National Taiwan University (NTU), Taipei, Taiwan 108Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, Thailand 109Cukurova University, Adana, Turkey 110Middle East Technical University, Physics Department, Ankara, Turkey 111Bogazici University, Istanbul, Turkey 112Istanbul Technical University, Istanbul, Turkey 113National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine 114University of Bristol, Bristol, United Kingdom 115Rutherford Appleton Laboratory, Didcot, United Kingdom 116Imperial College, London, United Kingdom 117Brunel University, Uxbridge, United Kingdom 118Baylor University, Waco, Texas 76798, USA 119The University of Alabama, Tuscaloosa, Alabama 35487, USA 120Boston University, Boston, Massachusetts 02215, USA 121Brown University, Providence, Rhode Island 02912, USA 122University of California, Davis, Davis, California 95616, USA 123University of California, Los Angeles, California 90095, USA 124University of California, Riverside, Riverside, California 92521, USA 125University of California, San Diego, La Jolla, California 92093, USA 126University of California, Santa Barbara, Santa Barbara, California 93106, USA PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-14 127California Institute of Technology, Pasadena, California 91125, USA 128Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA 129University of Colorado at Boulder, Boulder, Colorado 80309, USA 130Cornell University, Ithaca, New York 14853, USA 131Fairfield University, Fairfield, Connecticut 06430, USA 132Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA 133University of Florida, Gainesville, Florida 32611, USA 134Florida International University, Miami, Florida 33199, USA 135Florida State University, Tallahassee, Florida 32306, USA 136Florida Institute of Technology, Melbourne, Florida 32901, USA 137University of Illinois at Chicago (UIC), Chicago, Illinois 60607, USA 138The University of Iowa, Iowa City, Iowa 52242, USA 139Johns Hopkins University, Baltimore, Maryland 21218, USA 140The University of Kansas, Lawrence, Kansas 66045, USA 141Kansas State University, Manhattan, Kansas 66506, USA 142Lawrence Livermore National Laboratory, Livermore, California 94551, USA 143University of Maryland, College Park, Maryland 20742, USA 144Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 145University of Minnesota, Minneapolis, Minnesota 55455, USA 146University of Mississippi, Oxford, Mississippi 38677, USA 147University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA 148State University of New York at Buffalo, Buffalo, New York 14260, USA 149Northeastern University, Boston, Massachusetts 02115, USA 150Northwestern University, Evanston, Illinois 60208, USA 151University of Notre Dame, Notre Dame, Indiana 46556, USA 152The Ohio State University, Columbus, Ohio 43210, USA 153Princeton University, Princeton, New Jersey 08542, USA 154University of Puerto Rico, Mayaguez, Puerto Rico 00681, USA 155Purdue University, West Lafayette, Indiana 47907, USA 156Purdue University Calumet, Hammond, Indiana 46323, USA 157Rice University, Houston, Texas 77251, USA 158University of Rochester, Rochester, New York 14627, USA 159The Rockefeller University, New York, New York 10021, USA 160Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA 161University of Tennessee, Knoxville, Tennessee 37996, USA 162Texas A&M University, College Station, Texas 77843, USA 163Texas Tech University, Lubbock, Texas 79409, USA 164Vanderbilt University, Nashville, Tennessee 37235, USA 165University of Virginia, Charlottesville, Virginia 22904, USA 166Wayne State University, Detroit, Michigan 48202, USA 167University of Wisconsin, Madison, Wisconsin 53706, USA aDeceased. bAlso at Vienna University of Technology, Vienna, Austria. cAlso at CERN, European Organization for Nuclear Research, Geneva, Switzerland. dAlso at Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France. eAlso at National Institute of Chemical Physics and Biophysics, Tallinn, Estonia. fAlso at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow, Russia. gAlso at Universidade Estadual de Campinas, Campinas, Brazil. hAlso at Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France. iAlso at Université Libre de Bruxelles, Bruxelles, Belgium. jAlso at Joint Institute for Nuclear Research, Dubna, Russia. kAlso at Suez University, Suez, Egypt. lAlso at Cairo University, Cairo, Egypt. mAlso at Fayoum University, El-Fayoum, Egypt. nAlso at British University in Egypt, Cairo, Egypt. oAlso at Ain Shams University, Cairo, Egypt. pAlso at Université de Haute Alsace, Mulhouse, France. qAlso at Brandenburg University of Technology, Cottbus, Germany. PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-15 rAlso at Institute of Nuclear Research ATOMKI, Debrecen, Hungary. sAlso at Eötvös Loránd University, Budapest, Hungary. tAlso at University of Debrecen, Debrecen, Hungary. uAlso at University of Visva-Bharati, Santiniketan, India. vAlso at King Abdulaziz University, Jeddah, Saudi Arabia. wAlso at University of Ruhuna, Matara, Sri Lanka. xAlso at Isfahan University of Technology, Isfahan, Iran. yAlso at University of Tehran, Department of Engineering Science, Tehran, Iran. zAlso at Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran, Iran. aaAlso at Università degli Studi di Siena, Siena, Italy. bbAlso at Centre National de la Recherche Scientifique (CNRS) - IN2P3, Paris, France. ccAlso at Purdue University, West Lafayette, USA. ddAlso at International Islamic University of Malaysia, Kuala Lumpur, Malaysia. eeAlso at Institute for Nuclear Research, Moscow, Russia. ffAlso at St. Petersburg State Polytechnical University, St. Petersburg, Russia. ggAlso at California Institute of Technology, Pasadena, USA. hhAlso at Faculty of Physics, University of Belgrade, Belgrade, Serbia. iiAlso at Facoltà Ingegneria, Università di Roma, Roma, Italy. jjAlso at Scuola Normale e Sezione dell’INFN, Pisa, Italy. kkAlso at University of Athens, Athens, Greece. llAlso at Paul Scherrer Institut, Villigen, Switzerland. mmAlso at Institute for Theoretical and Experimental Physics, Moscow, Russia. nnAlso at Albert Einstein Center for Fundamental Physics, Bern, Switzerland. ooAlso at Gaziosmanpasa University, Tokat, Turkey. ppAlso at Adiyaman University, Adiyaman, Turkey. qqAlso at Mersin University, Mersin, Turkey. rrAlso at Cag University, Mersin, Turkey. ssAlso at Piri Reis University, Istanbul, Turkey. ttAlso at Anadolu University, Eskisehir, Turkey. uuAlso at Ozyegin University, Istanbul, Turkey. vvAlso at Izmir Institute of Technology, Izmir, Turkey. wwAlso at Necmettin Erbakan University, Konya, Turkey. xxAlso at Mimar Sinan University, Istanbul, Istanbul, Turkey. yyAlso at Marmara University, Istanbul, Turkey. zzAlso at Kafkas University, Kars, Turkey. aaaAlso at Yildiz Technical University, Istanbul, Turkey. bbbAlso at Rutherford Appleton Laboratory, Didcot, United Kingdom. cccAlso at School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom. dddAlso at University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia. eeeAlso at Argonne National Laboratory, Argonne, USA. fffAlso at Erzincan University, Erzincan, Turkey. gggAlso at Texas A&M University at Qatar, Doha, Qatar. hhhAlso at Kyungpook National University, Daegu, Korea. PRL 114, 191802 (2015) P HY S I CA L R EV I EW LE T T ER S week ending 15 MAY 2015 191802-16