Compact Muon Solenoid
LHC, CERN
Visit us: CMS Public Website, CMS Physics ;
Contact us: CMS Publications Committee
| CMS-HIN-18-008 ; CERN-EP-2021-100 | ||
| Two-particle azimuthal correlations in $\gamma$p interactions using pPb collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV | ||
| CMS Collaboration | ||
| 28 April 2022 | ||
| Phys. Lett. B 844 (2023) 137905 | ||
| Abstract: The first measurements of the Fourier coefficients (${V_{n\Delta}}$) of the azimuthal distributions of charged hadrons emitted from photon-proton ($\gamma$p) interactions are presented. The data are extracted from 68.8 nb$^{-1}$ of ultra-peripheral proton-lead (pPb) collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV using the CMS detector. The high energy lead ions produce a flux of photons that can interact with the oncoming proton. This $\gamma$p system provides a set of unique initial conditions with multiplicity lower than in photon-lead collisions but comparable to recent electron-positron and electron-proton data. The ${V_{n\Delta}}$ coefficients are presented in ranges of event multiplicity and transverse momentum (${p_{\mathrm{T}}}$) and are compared to corresponding hadronic minimum bias pPb results. For a given multiplicity range, the mean ${p_{\mathrm{T}}}$ of charged particles is smaller in $\gamma$p than in pPb collisions. For both the $\gamma$p and pPb samples, ${{V_{1\Delta}}}$ is negative, ${{V_{2\Delta}}}$ is positive, and ${{V_{3\Delta}}}$ consistent with 0. For each multiplicity and ${p_{\mathrm{T}}}$ range, ${{V_{2\Delta}}}$ is larger for $\gamma$p events. The $\gamma$p data are consistent with model predictions that have no collective effects thus suggesting the absence of collectivity in the $\gamma$p system over the multiplicity range explored in this work. | ||
| Links: e-print arXiv:2204.13486 [nucl-ex] (PDF) ; CDS record ; inSPIRE record ; HepData record ; CADI line (restricted) ; | ||
| Figures | |
png pdf |
Figure 1:
The ${N_{\text {trk}}}$ spectra for $\gamma$p and MB samples. The simulated $\gamma$p distribution has been normalized to the same event yield of the data $\gamma$p enhanced sample. |
png pdf |
Figure 2:
Two-dimensional (left) and one-dimensional (right) correlation plots for $\gamma$p-enhanced (upper) and MB (lower) events for 0.3 $ < {p_{\mathrm {T}}} < $ 3.0 GeV/$c$ and 2 $\leq {N_{\text {trk}}} < $ 35. For the two-dimensional distributions, the jet peak centered at $ {{\Delta \eta}} = {{\Delta \phi}} = $ 0 is truncated to increase visibility. The rapidity gap requirement for the $\gamma$p-enhanced sample limits the $ {| \Delta \eta |}$ range to $ {| \Delta \eta |} <$ 2.5. The one-dimensional ${{\Delta \phi}}$ distributions are symmetrized by construction around $ {{\Delta \phi}} = $ 0 and $\pi $. The Fourier coefficients, ${V_{n\Delta}}$ in the right column are fit over the $ {{\Delta \phi}} $ range [0, $\pi $]. Points outside this range are shown as open circles and are obtained by symmetrization of those in [0, $\pi $]. Statistical error bars are shown for both one-dimensional distributions. |
png pdf |
Figure 3:
Dependence of ${V_{n\Delta}}$ on ${N_{\text {trk}}}$ for $\gamma$p and MB events for two different ${p_{\mathrm {T}}}$ ranges. Systematic uncertainties are shown by the shaded bars in the two panels. The 2 $\le {N_{\text {trk}}} < $ 5, 5 $ \le {N_{\text {trk}}} < $ 10, 10 $\le {N_{\text {trk}}} < $ 35 are used for the lower ${p_{\mathrm {T}}}$ range and 2 $\leq {N_{\text {trk}}} <$ 5 and 5 $\leq {N_{\text {trk}}} < $ 35 for the higher range. The points are placed at the mean value of the corresponding ${N_{\text {trk}}}$ range. Lines indicate the prediction for $\gamma$p events from PYTHIA8. |
png pdf |
Figure 4:
Single-particle azimuthal anisotropy ${v_2}$ versus ${N_{\text {trk}}}$ for $\gamma$p-enhanced and pPb samples in two ${p_{\mathrm {T}}}$ regions. Systematic uncertainties are shown by the shaded bars in the two panels. Predictions from the PYTHIA8 and HIJING generators are shown for the $\gamma$p and MB pPb samples respectively. For the $\gamma$p events, same ${N_{\text {trk}}}$ bin arrangement as in Figure 3 is kept while for pPb the bins [2, 5), [5, 10), [10, 15) and [15, 20) are used. |
| Tables | |
png pdf |
Table 1:
Mean ${N_{\text {trk}}}$ for the $\gamma$p-enhanced and the MB data sets for five classes of ${N_{\text {trk}}}$. Statistical uncertainties are negligible. |
png pdf |
Table 2:
The ${V_{n\Delta}}$ coefficients for $\gamma$p-enhanced events, as functions of ${p_{\mathrm {T}}}$ and ${N_{\text {trk}}}$. Statistical and systematic uncertainties are added in quadrature. |
| Summary |
| For the first time, the study of long-range particle correlations has been extended to photon-proton ($\gamma$p) interactions. This study used proton-lead (pPb) collisions at ${\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV recorded with the CMS detector. The two-particle ${V_{n\Delta}}$ Fourier coefficients and corresponding single-particle ${v_2}$ azimuthal anisotropies are reported as functions of the multiplicity of charged hadrons (${N_{\text{trk}}}$) for two transverse momentum (${p_{\mathrm{T}}}$) ranges. For the $\gamma$p sample, the largest observed multiplicity was ${N_{\text{trk}}} \sim$ 3. The mean ${p_{\mathrm{T}}}$ of charged particles is smaller in the $\gamma$p sample than for pPb collisions within the same multiplicity range. No evidence for a long-range near-side ridge-like structure was found for either the $\gamma$p or hadronic minimum bias pPb (MB) samples within this multiplicity range. In all ${N_{\text{trk}}}$ and ${p_{\mathrm{T}}}$ ranges, ${{V_{1\Delta}}}$ is negative, ${{V_{2\Delta}}}$ is positive with a smaller magnitude than ${{V_{1\Delta}}}$, and ${{V_{3\Delta}}}$ is consistent with zero. The magnitudes of both ${{V_{1\Delta}}}$ and ${{V_{2\Delta}}}$ increase with ${p_{\mathrm{T}}}$. This increase has also been seen in electron-proton collisions. At a given ${p_{\mathrm{T}}}$ and track multiplicity, ${v_2}$ is larger for $\gamma$p-enhanced events than for MB pPb interactions. Predictions from the {PYTHIA}8 and HIJING models describe well the $\gamma$p and pPb MB data at low ${p_{\mathrm{T}}}$, but slightly overestimate the data at higher ${p_{\mathrm{T}}}$. Since these models do not have collective effects, these data suggest the absence of collectivity in the $\gamma$p system over the multiplicity range explored in this work. |
| References | ||||
| 1 | CMS Collaboration | Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC | JHEP 09 (2010) 091 | CMS-QCD-10-002 1009.4122 |
| 2 | ATLAS Collaboration | Observation of long-range elliptic azimuthal anisotropies in $ \sqrt{s} $ = 13 and 2.76 TeV pp collisions with the ATLAS detector | PRL 116 (2016) 172301 | 1509.04776 |
| 3 | CMS Collaboration | Measurement of long-range near-side two-particle angular correlations in pp collisions at $ \sqrt{s} = $ 13 TeV | PRL 116 (2015) 172302 | CMS-FSQ-15-002 1510.03068 |
| 4 | CMS Collaboration | Evidence for collectivity in pp collisions at the LHC | PLB 765 (2017) 193 | CMS-HIN-16-010 1606.06198 |
| 5 | ATLAS Collaboration | Measurement of azimuthal anisotropy of muons from charm and bottom hadrons in pp collisions at $ \sqrt{s} = $ 13 TeV with the ATLAS detector | PRL 124 (2020) 082301 | 1909.01650 |
| 6 | CMS Collaboration | Observation of long-range near-side angular correlations in pPb collisions at the LHC | PLB 718 (2013) 795 | CMS-HIN-12-015 1210.5482 |
| 7 | PHENIX Collaboration | Measurement of long-range angular correlations and azimuthal anisotropies in high-multiplicity p$ + $Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 200 GeV | PRC 95 (2017) 034910 | 1609.02894 |
| 8 | PHENIX Collaboration | Creation of quark-gluon plasma droplets with three distinct geometries | NP 15 (2019) 214 | 1805.02973 |
| 9 | ATLAS Collaboration | Observation of associated near-side and away-side long-range correlations in $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV proton-lead collisions with the ATLAS detector | PRL 110 (2013) 182302 | 1212.5198 |
| 10 | ATLAS Collaboration | Measurement with the ATLAS detector of multi-particle azimuthal correlations in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 725 (2013) 60 | 1303.2084 |
| 11 | ALICE Collaboration | Long-range angular correlations on the near and away side in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 719 (2013) 29 | 1212.2001 |
| 12 | LHCb Collaboration | Measurements of long-range near-side angular correlations in $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5 TeV proton-lead collisions in the forward region | PLB 762 (2016) 473 | 1512.00439 |
| 13 | ALICE Collaboration | Long-range angular correlations of $ \pi $, K and p in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 726 (2013) 164 | 1307.3237 |
| 14 | CMS Collaboration | Evidence for collective multiparticle correlations in pPb collisions | PRL 115 (2015) 012301 | CMS-HIN-14-006 1502.05382 |
| 15 | CMS Collaboration | Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies | PLB 742 (2015) 200 | CMS-HIN-14-002 1409.3392 |
| 16 | ATLAS Collaboration | Measurement of multi-particle azimuthal correlations in pp, pPb and low multiplicity PbPb collisions with the ATLAS detector | EPJC. 77 (2017) 428 | 1705.04176 |
| 17 | ATLAS Collaboration | Measurement of long-range multiparticle azimuthal correlations with the subevent cumulant method in pp and pPb collisions with the ATLAS detector at the CERN large hadron collider | PRC 97 (2018) 024904 | 1708.03559 |
| 18 | J.-Y. Ollitrault | Anisotropy as a signature of transverse collective flow | PRD 46 (1992) 229 | |
| 19 | U. Heinz and R. Snellings | Collective flow and viscosity in relativistic heavy-ion collisions | Ann. Rev. Nucl. Part. Sci. 63 (2013) 123 | 1301.2826 |
| 20 | C. Gale, S. Jeon, and B. Schenke | Hydrodynamic modeling of heavy-ion collisions | Int. J. Mod. Phys. A 28 (2013) 1340011 | 1301.5893 |
| 21 | K. Dusling, W. Li, and B. Schenke | Novel collective phenomena in high-energy proton--proton and proton--nucleus collisions | Int. J. Mod. Phys. E 25 (2016) 1630002 | 1509.07939 |
| 22 | J. L. Nagle and J. Orjuela Koop | A quasiparticle transport explanation for collectivity in the smallest of collision systems (pp and e$^+$e$^-$) | NP A 982 (2019) 455 | 1807.04619 |
| 23 | STAR Collaboration | Elliptic flow in AuAu collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 130 GeV | PRL 86 (2001) 402 | nucl-ex/0009011 |
| 24 | PHOBOS Collaboration | System size dependence of cluster properties from two-particle angular correlations in Cu+Cu and Au+Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 200 GeV | PRC 81 (2010) 024904 | 0812.1172 |
| 25 | CMS Collaboration | Long-range and short-range dihadron angular correlations in central PbPb collisions at a nucleon-nucleon center of mass energy of 2.76 TeV | JHEP 10 (2011) 076 | CMS-HIN-11-001 1105.2438 |
| 26 | CMS Collaboration | Centrality dependence of dihadron correlations and azimuthal anisotropy harmonics in PbPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | EPJC 72 (2012) 10052 | CMS-HIN-11-006 1201.3158 |
| 27 | ALICE Collaboration | Harmonic decomposition of two-particle angular correlations in Pb-Pb collisions at $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 2.76 TeV | --264, 2012 PLB 708 (2012) 249 |
1109.2501 |
| 28 | ATLAS Collaboration | Measurement of the azimuthal anisotropy for charged particle production in $ \sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}= $ 2.76 TeV lead-lead collisions with the ATLAS detector | Phys. Rev. C 86 (2012) 014907 | 1203.3087 |
| 29 | STAR Collaboration | Long range rapidity correlations and jet production in high energy nuclear collisions | PRC 80 (2009) 064912 | 0909.0191 |
| 30 | STAR Collaboration | Three-particle coincidence of the long range pseudorapidity correlation in high energy nucleus-nucleus collisions | PRL 105 (2010) 022301 | 0912.3977 |
| 31 | PHENIX Collaboration | Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration | NP A 757 (2005) 184 | nucl-ex/0410003 |
| 32 | STAR Collaboration | Beam-energy dependence of identified two-particle angular correlations in $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}=$ 7.7-200 GeV Au+Au collisions | PRC 101 (2020) 014916 | 1906.09204 |
| 33 | STAR Collaboration | Correlation measurements between flow harmonics in Au+Au collisions at RHIC | PLB 783 (2018) 459 | 1803.03876 |
| 34 | S. Voloshin and Y. Zhang | Flow study in relativistic nuclear collisions by fourier expansion of azimuthal particle distributions | PRC. 70 (1996) 665 | hep-ph/9407282 |
| 35 | B. H. Alver, C. Gombeaud, M. Luzum, and J.-Y. Ollitrault | Triangular flow in hydrodynamics and transport theory | PRC 82 (2010) 034913 | 1007.5469 |
| 36 | C. G. B. Schenke, S. Jeon | Elliptic and triangular flow in event-by-event $ D=$ 3+1 viscous hydrodynamics | PRLett 106 (2011) 042301 | 1009.3244 |
| 37 | C. S. Z. Qiu and U. Heinz | Hydrodynamic elliptic and triangular flow in Pb-Pb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 2.76 TeV | PLB 707 (2012) 151 | 1110.3033 |
| 38 | B. Alver and G. Roland | Collision geometry fluctuations and triangular flow in heavy-ion collisions | PRC 81 (2010) 054905 | 1003.0194 |
| 39 | CMS Collaboration | Elliptic flow of charm and strange hadrons in high-multiplicity pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 8.16 TeV | PRL 121 (2018) 082301 | CMS-HIN-17-003 1804.09767 |
| 40 | CMS Collaboration | Centrality and pseudorapidity dependence of the transverse energy density in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PRC 100 (2019) 024902 | CMS-HIN-14-014 1810.05745 |
| 41 | ALICE Collaboration | Multi-strange baryon production in pPb collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}} = $ 5.02 TeV | PLB 758 (2016) 389 | 1512.07227 |
| 42 | PHENIX Collaboration | Elliptic flow of identified hadrons in Au+Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 200 GeV | PRL 91 (2003) 182301 | nucl-ex/0305013 |
| 43 | STAR Collaboration | Distributions of charged hadrons associated with high transverse momentum particles in pp and Au+Au collisions at $ {\sqrt {\smash [b]{s_{_{\mathrm {NN}}}}}}= $ 200 GeV | PRL 95 (2005) 152301 | nucl-ex/0501016 |
| 44 | R. D. Weller and P. Romatschke | One fluid to rule them all: viscous hydrodynamic description of event-by-event central p+p, p+Pb and Pb+Pb collisions at $ \sqrt{s} = $ 5.02 TeV | PLB 774 (2017) 351 | 1701.07145 |
| 45 | P. Bozek | Collective flow in pPb and d-Pb collisions at TeV energies | PRC 85 (2012) 014911 | 1112.0915 |
| 46 | P. Bozek and W. Broniowski | Correlations from hydrodynamic flow in pPb collisions | PLB 718 (2013) 1557 | 1211.0845 |
| 47 | P. Bozek and W. Broniowski | Collective dynamics in high-energy proton-nucleus collisions | PRC 88 (2013), no. 1, 014903 | 1304.3044 |
| 48 | A. Badea et al. | Measurements of two-particle correlations in e$^+$e$^-$ collisions at 91 GeV with ALEPH archived data | PRL 123 (2019) 212002 | 1906.00489 |
| 49 | Belle Collaboration | Measurement of Two-Particle Correlations of Hadrons in e+e- Collisions at Belle | no.~14, 14, 2022 PRL 128 (2022) |
2201.01694 |
| 50 | ZEUS Collaboration | Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic ep scattering at HERA | JHEP 04 (2020) 070 | 1912.07431 |
| 51 | ZEUS Collaboration | Azimuthal correlations in photoproduction and deep inelastic $ ep $ scattering at HERA | JHEP 12 (2021) 102 | 2106.12377 |
| 52 | ATLAS Collaboration | Two-particle azimuthal correlations in photonuclear ultraperipheral PbPb collisions at 5.02 TeV with ATLAS | PRC 104 (2021) 014903 | 2101.10771 |
| 53 | A. J. Baltz | The physics of ultraperipheral collisions at the LHC | PR 458 (2008) 1 | 0706.3356 |
| 54 | C. F. von Weizsacker | Radiation emitted in collisions of very fast electrons | Z. Phys. 88 (1934) 612 | |
| 55 | E. J. Williams | Nature of the high-energy particles of penetrating radiation and status of ionization and radiation formulae | PR45 (1934) 729 | |
| 56 | E. Fermi | On the theory of collisions between atoms and electrically charged particles | Nuovo Cim. 2 (1925) 143 | hep-th/0205086 |
| 57 | CMS Collaboration | Observation of correlated azimuthal anisotropy fourier harmonics in pp and pPb collisions at the LHC | PRL 120 (2018) 092301 | CMS-HIN-16-022 1709.09189 |
| 58 | I. Helenius and C. O. Rasmussen | Hard diffraction in photoproduction with PYTHIA 8 | EPJC 79 (2019), no. 5, 413 | 1901.05261 |
| 59 | DELPHES 3 Collaboration | DELPHES 3, a modular framework for fast simulation of a generic collider experiment | JHEP 02 (2014) 057 | 1307.6346 |
| 60 | X.-N. Wang and M. Gyulassy | HIJING: A monte carlo model for multiple jet production in pp, pA and AA collisions | PRD 44 (1991) 3501 | |
| 61 | GEANT4 Collaboration | GEANT4--a simulation toolkit | NIMA 506 (2003) 250 | |
| 62 | O. Surányi et al. | Performance of the CMS Zero Degree Calorimeters in pPb collisions at the LHC | no.~05, P05008, 2021 JINST 16 (2021) |
2102.06640 |
| 63 | CMS Collaboration | Particle-flow reconstruction and global event description with the CMS detector | JINST 12 (2017) P10003 | CMS-PRF-14-001 1706.04965 |
| 64 | CMS Collaboration | The CMS experiment at the CERN LHC | JINST 3 (2008) S08004 | CMS-00-001 |
| 65 | 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 |
| 66 | CMS Collaboration | The CMS trigger system | JINST 12 (2017) P01020 | CMS-TRG-12-001 1609.02366 |
| 67 | CMS Collaboration | Pseudorapidity distributions of charged hadrons in proton-lead collisions at $ \sqrt{s_{_\mathrm{NN}}}= $ 5.02 and 8.16 TeV | JHEP 01 (2018) 045 | CMS-HIN-16-021 1710.09355 |
| 68 | CMS Collaboration | First measurement of the forward rapidity gap distribution in pPb collisions at $ \sqrt{s_{_\mathrm{NN}}} = $ 8.16 TeV | CMS-PAS-HIN-18-019 | CMS-PAS-HIN-18-019 |
| 69 | ATLAS Collaboration | Rapidity gap cross sections measured with the ATLAS detector in pp collisions at $ \sqrt{s} = $ 7 TeV | EPJC 72 (2012) 1926 | 1201.2808 |
| 70 | CMS Collaboration | Measurement of diffraction dissociation cross sections in pp collisions at $ \sqrt{s} = $ 7 TeV | PRD 92 (2015) 012003 | CMS-FSQ-12-005 1503.08689 |
| 71 | J. D. Bjorken | Rapidity gaps and jets as a new physics signature in very high-energy hadron hadron collisions | PRD 47 (1993) 101 | |
| 72 | CMS Collaboration | Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions | PLB 724 (2013) 213 | CMS-HIN-13-002 1305.0609 |
| 73 | H. Mäntysaari, B. Schenke, C. Shen, and P. Tribedy | Imprints of fluctuating proton shapes on flow in proton-lead collisions at the LHC | PLB 772 (2017) 681 | 1705.03177 |
| 74 | CMS Collaboration | HEPData record for this analysis | link | |
|
|
Compact Muon Solenoid LHC, CERN |
|
|
|
|
|
|