Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-HIN-12-009 ; CERN-EP-2016-098 | ||
| Coherent $\mathrm{ J } / \psi $ photoproduction in ultra-peripheral PbPb collisions at $\sqrt{s_{ \mathrm{NN}}} = $ 2.76 TeV with the CMS experiment | ||
| CMS Collaboration | ||
| 23 May 2016 | ||
| Phys. Lett. B 772 (2017) 489 | ||
| Abstract: The cross section for coherent $\mathrm{ J } / \psi$ photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, $X_{\mathrm{n}}0_{\mathrm{n}}$, is measured with the CMS experiment in ultra-peripheral PbPb collisions at $\sqrt{s_{ \mathrm{NN}}} = $ 2.76 TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159 $\mu$b$^{-1}$, collected during the 2011 PbPb run. The $\mathrm{ J } / \psi$ mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is $\mathrm{d}\sigma^{\text{coh}}_{X_{\mathrm{n}}0_{\mathrm{n}}}/{\mathrm{d} y}( \mathrm{ J } / \psi ) =$ 0.36 $\pm$ 0.04 (stat) $\pm$ 0.04 (syst) mb in the rapidity interval 1.8 $ < |{y}| < $ 2.3 . Using a model for the relative rate of coherent photoproduction processes, this $X_{\mathrm{n}}0_{\mathrm{n}}$ measurement gives a total coherent photoproduction cross section of ${\mathrm{d}\sigma^{\text{coh}}}/{\mathrm{d} y}( \mathrm{ J } / \psi ) =$ 1.82 $\pm$ 0.22 (stat) $\pm$ 0.20 (syst) $\pm$ 0.19 (theo) mb. The data strongly disfavour the impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent $\mathrm{ J } / \psi$ photoproduction in $\gamma $+Pb interactions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing. | ||
| Links: e-print arXiv:1605.06966 [nucl-ex] (PDF) ; CDS record ; inSPIRE record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1-a:
Results from the simultaneous fit to dimuon invariant mass (a) and $ {p_{\mathrm {T}}} $ (b) distributions from opposite-sign muon pairs with $ {p_{\mathrm {T}}} < $ 1.0 GeV, 1.8 $ < {| y | }< $ 2.3 and 2.6 $ |
png pdf |
Figure 1-b:
Results from the simultaneous fit to dimuon invariant mass (a) and $ {p_{\mathrm {T}}} $ (b) distributions from opposite-sign muon pairs with $ {p_{\mathrm {T}}} < $ 1.0 GeV, 1.8 $ < {| y | }< $ 2.3 and 2.6 $ |
png pdf |
Figure 2:
Differential cross section versus rapidity for coherent $ {\mathrm{ J } / \psi } $ production in ultra-peripheral PbPb collisions at $\sqrt {s_{ \mathrm{NN}}}= $ 2.76 TeV , measured by ALICE [29,30] and CMS (see text for details). The vertical error bars include the statistical and systematic uncertainties added in quadrature, and the horizontal bars represent the range of the measurements in $y$. Also the impulse approximation and the leading twist approximation calculations are shown (see text for details). |
| Tables | |
png pdf |
Table 1:
Summary of systematic uncertainties for coherent $ {\mathrm{ J } / \psi } $ events in the $ {X_{\mathrm {n}}0_{\mathrm {n}}} $ configuration. |
| Summary |
|
The coherent $\mathrm{ J } / \psi$ photoproduction cross section in ultra-peripheral PbPb collisions at $\sqrt{s_{ \mathrm{NN}}} =$ 2.76 TeV, in conjunction with at least one neutron on one side of the interaction point and no neutron activity on the other side, is measured to be ${\mathrm{d}\sigma^{\text{coh}}_{X_{\mathrm{n}}0_{\mathrm{n}}}}/{\mathrm{d} y}( \mathrm{ J } / \psi ) =$ 0.36 $\pm$ 0.04 (stat) $\pm$ 0.04 (syst) mb in the rapidity interval 1.8 $ < |{y}| < $ 2.3 . This measurement is extrapolated to the total coherent $\mathrm{ J } / \psi$ cross section, resulting in ${\mathrm{d}\sigma^{\text{coh}}}/{\mathrm{d} y}( \mathrm{ J } / \psi ) =$ 1.82 $\pm$ 0.22 (stat) $\pm$ 0.20 (syst) $\pm$ 0.19 (theo) mb in the measured rapidity interval. These results complement recent measurements on coherent $\mathrm{ J } / \psi$ photoproduction in ultra-peripheral PbPb collisions at $\sqrt{s_{ \mathrm{NN}}} =$ 2.76 TeV by the ALICE collaboration. An impulse approximation model prediction is strongly disfavored, indicating that nuclear effects expected to be present at low $x$ and $Q^2$ values are needed to describe the data. The prediction given by the leading twist approximation, which includes nuclear gluon shadowing, is consistent with the data. |
| References | ||||
| 1 | C. A. Bertulani, S. R. Klein, and J. Nystrand | Physics of ultra-peripheral nuclear collisions | Ann. Rev. Nucl. Part. Sci. 55 (2005) 271 | nucl-ex/0502005 |
| 2 | A. J. Baltz | The physics of ultraperipheral collisions at the LHC | PR 458 (2008) 1 | 0706.3356 |
| 3 | J. G. Contreras and J. D. Tapia Takaki | Ultra-peripheral heavy-ion collisions at the LHC | Int. J. Mod. Phys. A 30 (2015) 1542012 | |
| 4 | H1 Collaboration | Elastic $ \mathrm{J} / \psi $ production at HERA | EPJC 46 (2006) 585 | hep-ex/0510016 |
| 5 | ZEUS Collaboration | Exclusive photoproduction of $ \mathrm{J} / \psi $ mesons at HERA | EPJC 24 (2002) 345 | hep-ex/0201043 |
| 6 | CDF Collaboration | Observation of exclusive charmonium production and $ \gamma\gamma\rightarrow $ $ \mu^+\mu^- $ in $ \mathrm{p\bar{p}} $ collisions at $ \sqrt{s} = 1.96 $ TeV | PRL 102 (2009) 242001 | 0902.1271 |
| 7 | ALICE Collaboration | Exclusive $ \mathrm{J} / \psi $ photoproduction off protons in ultra-peripheral p-Pb collisions at $ \sqrt{s_{\rm NN}}=5.02 $ TeV | PRL 113 (2014) 232504 | 1406.7819 |
| 8 | LHCb Collaboration | Updated measurements of exclusive $ \mathrm{J} / \psi $ and $ \psi $(2S) production cross-sections in pp collisions at $ \sqrt{s}=7 $ TeV | JPG 41 (2014) 055002 | 1401.3288 |
| 9 | M. G. Ryskin | Diffractive $ \mathrm{J} / \psi $ electroproduction in LLA QCD | Z. Phys. C 57 (1993) 89 | |
| 10 | S. J. Brodsky et al. | Diffractive leptoproduction of vector mesons in QCD | PRD 50 (1994) 3134 | hep-ph/9402283 |
| 11 | A. Adeluyi and C. A. Bertulani | Constraining gluon shadowing using photoproduction in ultraperipheral pA and AA Collisions | PRC 85 (2012) 044904 | 1201.0146 |
| 12 | A. Adeluyi and T. Nguyen | Coherent photoproduction of $ \mathrm{J} / \psi $ and $ \Upsilon $ mesons in ultraperipheral pPb and PbPb collisions at the CERN LHC | PRC 87 (2013) 027901 | 1302.4288 |
| 13 | A. Cisek, W. Schafer, and A. Szczurek | Exclusive coherent production of heavy vector mesons in nucleus-nucleus collisions at LHC | PRC 86 (2012) 014905 | 1204.5381 |
| 14 | S. Klein and J. Nystrand | Exclusive vector meson production in relativistic heavy ion collisions | PRC 60 (1999) 014903 | hep-ph/9902259 |
| 15 | T. Lappi and H. Mantysaari | $ \mathrm{J} / \psi $ production in ultraperipheral Pb+Pb and p+Pb collisions at energies available at the CERN Large Hadron Collider | PRC 87 (2013) 032201 | 1301.4095 |
| 16 | V. P. Goncalves and M. V. T. Machado | Vector meson production in coherent hadronic interactions: An update on predictions for RHIC and LHC | PRC 84 (2011) 011902 | 1106.3036 |
| 17 | V. Rebyakova, M. Strikman, and M. Zhalov | Coherent $ \rho^{0} $ and $ \mathrm{J} / \psi $ photoproduction in ultraperipheral processes with electromagnetic dissociation of heavy ions at RHIC and LHC | PLB 710 (2012) 647 | 1109.0737 |
| 18 | V. Guzey, M. Strikman, and M. Zhalov | Disentangling coherent and incoherent quasielastic $ \mathrm{J} / \psi $ photoproduction on nuclei by neutron tagging in ultraperipheral ion collisions at the LHC | EPJC 74 (2014) 2942 | 1312.6486 |
| 19 | \relax Yu. P. Ivanov, B. Z. Kopeliovich, and I. Schmidt | Vector meson production in ultra-peripheral collisions at LHC | in Workshop on Heavy Ion Collisions at the LHC: Last Call for Predictions Geneva, Switzerland, May 14-June 8, 2007 2007 | 0706.1532 |
| 20 | B. L. Berman and S. C. Fultz | Measurements of the giant dipole resonance with monoenergetic photons | Rev. Mod. Phys. 47 (1975) 713 | |
| 21 | A. Accardi et al. | Electron ion collider: The next QCD frontier - understanding the glue that binds us all | 1212.1701 | |
| 22 | J. L. Abelleira Fernandez et al. | A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector | JPG 39 (2012) 075001 | 1206.2913 |
| 23 | Y. Akiba et al. | The hot QCD white paper: Exploring the phases of QCD at RHIC and the LHC | 1502.02730 | |
| 24 | K. J. Eskola, H. Paukkunen, and C. A. Salgado | EPS09: A new generation of NLO and LO nuclear parton distribution functions | JHEP 04 (2009) 065 | 0902.4154 |
| 25 | S. P. Jones, A. D. Martin, M. G. Ryskin, and T. Teubner | Exclusive $ \mathrm{J} / \psi $ and $ \Upsilon $ photoproduction and the low $ x $ gluon | JPG 43 (2016) 035002 | 1507.06942 |
| 26 | J. Rojo et al. | The PDF4LHC report on PDFs and LHC data: Results from run I and preparation for run II | JPG 42 (2015) 103103 | 1507.00556 |
| 27 | STAR Collaboration | $ \rho^{0} $ photoproduction in ultraperipheral relativistic heavy ion collisions at $ \sqrt{s_ \mathrm{NN}} $ = 200 GeV | PRC 77 (2008) 034910 | 0712.3320 |
| 28 | PHENIX Collaboration | Photoproduction of $ \mathrm{J} / \psi $ and of high mass $ \mathrm{e^{+}e^{-}} $ in ultra-peripheral Au+Au collisions at $ \sqrt{s_ \mathrm{NN}} $ = 200 GeV | PLB 679 (2009) 321 | 0903.2041 |
| 29 | ALICE Collaboration | Coherent $ \mathrm{J} / \psi $ photoproduction in ultra-peripheral Pb-Pb collisions at $ \sqrt{s_ \mathrm{NN}} = 2.76 $ TeV | PLB 718 (2013) 1273 | 1209.3715 |
| 30 | ALICE Collaboration | Charmonium and $ e^{+}e^{-} $ pair photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at $ \sqrt{s_{\rm NN}} $=2.76 TeV | EPJC 73 (2013) 2617 | 1305.1467 |
| 31 | V. Guzey, E. Kryshen, M. Strikman, and M. Zhalov | Evidence for nuclear gluon shadowing from the ALICE measurements of PbPb ultraperipheral exclusive $ \mathrm{J} / \psi $ production | PLB 726 (2013) 290 | 1305.1724 |
| 32 | K. J. Eskola, H. Paukkunen, and C. A. Salgado | An improved global analysis of nuclear parton distribution functions including RHIC data | JHEP 07 (2008) 102 | 0802.0139 |
| 33 | CMS Collaboration | Description and performance of track and primary-vertex reconstruction with the CMS tracker | JINST 9 (2014) P10009 | CMS-TRK-11-001 1405.6569 |
| 34 | CMS Collaboration | Performance of CMS muon reconstruction in pp collision events at $ \sqrt{s}=7 $ TeV | JINST 7 (2012) P10002 | CMS-MUO-10-004 1206.4071 |
| 35 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 36 | CMS Collaboration | Status of zero degree calorimeter for CMS experiment | AIP Conf. Proc. 867 (2006) 258 | nucl-ex/0608052 |
| 37 | CMS Collaboration | Measurement of the pseudorapidity and centrality dependence of the transverse energy density in PbPb collisions at $ \sqrt{s_ \mathrm{NN}} $ = 2.76 TeV | PRL 109 (2012) 152303 | CMS-HIN-11-003 1205.2488 |
| 38 | CMS Collaboration | Studies of azimuthal dihadron correlations in ultra-central PbPb collisions at $ \sqrt{s_ \mathrm{NN}} $ = 2.76 TeV | JHEP 02 (2014) 088 | CMS-HIN-12-011 1312.1845 |
| 39 | M. Chiu et al. | Measurement of mutual coulomb dissociation in $ \sqrt{s_ \mathrm{NN}} $ = 130 GeV Au+Au collisions at RHIC | PRL 89 (2002) 012302 | nucl-ex/0109018 |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|