Charged-particle multiplicity distributions over a wide pseudorapidity range in proton-proton collisions at $\mathbf{\sqrt{s}=}$ 0.9, 7 and 8 TeV

The ALICE collaboration Acharya, S. ; Adamová, D. ; Adolfsson, J. ; et al.
Eur.Phys.J.C 77 (2017) 852, 2017.
Inspire Record 1614477 DOI 10.17182/hepdata.78802

We present the charged-particle multiplicity distributions over a wide pseudorapidity range ($-3.4<\eta<5.0$) for pp collisions at $\sqrt{s}=$ 0.9, 7, and 8 TeV at the LHC. Results are based on information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE, extending the pseudorapidity coverage of the earlier publications and the high-multiplicity reach. The measurements are compared to results from the CMS experiment and to PYTHIA, PHOJET and EPOS LHC event generators, as well as IP-Glasma calculations.

90 data tables

Multiplicity distribution in the pseudorapidity region -2.0 to 2.0 for NSD collisions at a centre-of-mass energy of 900 GeV.

Multiplicity distribution in the pseudorapidity region -2.4 to 2.4 for NSD collisions at a centre-of-mass energy of 900 GeV.

Multiplicity distribution in the pseudorapidity region -3.0 to 3.0 for NSD collisions at a centre-of-mass energy of 900 GeV.

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Multiplicity dependence of two-particle azimuthal correlations in pp collisions at the LHC

The ALICE collaboration Abelev, Betty ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
JHEP 09 (2013) 049, 2013.
Inspire Record 1241570 DOI 10.17182/hepdata.62319

We present the measurements of particle pair yields per trigger particle obtained from di-hadron azimuthal correlations in pp collisions at $\sqrt{s} = 0.9$, $2.76$, and $7$ TeV recorded with the ALICE detector. The yields are studied as a function of the charged particle multiplicity. Taken together with the single particle yields the pair yields provide information about parton fragmentation at low transverse momenta, as well as on the contribution of multiple parton interactions to particle production. Data are compared to calculations using the PYTHIA6, PYTHIA8, and PHOJET event generators.

27 data tables

Per-trigger near-side pair yield for pT(trig) > 0.7 GeV and pT(assoc) > 0.4 GeV measured at sqrt(s) = 7 TeV.

Per-trigger near-side pair yield for pT(trig) > 0.7 GeV and pT(assoc) > 0.7 GeV measured at sqrt(s) = 7 TeV.

Per-trigger away-side pair yield for pT(trig) > 0.7 GeV and pT(assoc) > 0.4 GeV measured at sqrt(s) = 7 TeV.

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Centrality determination of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV with ALICE

The ALICE collaboration Abelev, Betty ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
Phys.Rev.C 88 (2013) 044909, 2013.
Inspire Record 1215085 DOI 10.17182/hepdata.66916

This publication describes the methods used to measure the centrality of inelastic Pb-Pb collisions at a center-of-mass energy of 2.76 TeV per colliding nucleon pair with ALICE. The centrality is a key parameter in the study of the properties of QCD matter at extreme temperature and energy density, because it is directly related to the initial overlap region of the colliding nuclei. Geometrical properties of the collision, such as the number of participating nucleons and number of binary nucleon-nucleon collisions, are deduced from a Glauber model with a sharp impact parameter selection, and shown to be consistent with those extracted from the data. The centrality determination provides a tool to compare ALICE measurements with those of other experiments and with theoretical calculations.

6 data tables

$N_\mathrm{part}$ for Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with the corresponding uncertainties derived from a Glauber calculation. The ${\langle N_\mathrm{part}^{\rm data} \rangle}$ are calculated from the NBD-Glauber fit to the VZERO amplitude, while the ${\langle N_\mathrm{part}^{\rm geo} \rangle}$ are obtained by slicing the impact parameter distribution. ${\langle N_\mathrm{part}^{\rm data} \rangle}$ is also calculated for two variations of the AP, i.e. moving it to 91 % (${\langle N_\mathrm{part}^{\rm data +} \rangle}$) and to 89 % (${\langle N_\mathrm{part}^{\rm data +} \rangle}$) respectively. The last three columns report the discrepancies between ${\langle N_\mathrm{part}^{\rm geo} \rangle}$ and ${\langle N_\mathrm{part}^{\rm data} \rangle}$ and ${\langle N_\mathrm{part}^{\rm data} \rangle}$ with the uncertainty of the AP.

Same as Table A.1 for $N_\mathrm{coll}$.

Same as Table A.1 for $T_\mathrm{AA}$.

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Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles in p-Pb Collisions at sqrt{s_NN} = 5.02 TeV

The ALICE collaboration Abelev, Betty ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
Phys.Rev.Lett. 110 (2013) 082302, 2013.
Inspire Record 1190895 DOI 10.17182/hepdata.37287

The transverse momentum ($p_{\mathrm T}$) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ALICE detector at the LHC. The $p_{\mathrm T}$ spectra measured near central rapidity in the range $0.5<p_{\mathrm T}<20$ GeV/$c$ exhibit a weak pseudorapidity dependence. The nuclear modification factor $R_{\mathrm{pPb}}$ is consistent with unity for $p_{\mathrm T}$ above 2 GeV/$c$. This measurement indicates that the strong suppression of hadron production at high $p_{\mathrm T}$ observed in Pb-Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations.

4 data tables

Normalized differential primary charged particle yield.

pp INEL cross section scaled by nuclear overlap.

Nuclear Modification Factor R_pPb in the central region.

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Net-Charge Fluctuations in Pb-Pb collisions at \surds_NN = 2.76 TeV

The ALICE collaboration Abelev, Betty ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
Phys.Rev.Lett. 110 (2013) 152301, 2013.
Inspire Record 1123802 DOI 10.17182/hepdata.60476

We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudorapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the fluctuations at LHC are smaller compared to the measurements at the Relativistic heavy Ion Collider (RHIC), and as such, closer to what has been theoretically predicted for the formation of Quark-Gluon Plasma (QGP).

7 data tables

The measured NU(+-DYN) as a function of the centrality of the collisions, expressed as the number of participating nucleons, for two values of midrapidity range.

NU(+-DYN), corrected for charge conservation and finite acceptance effects, as a function of the centrality of the collisions, expressed as the number of participating nucleons, for two values of midrapidity range.

The measured and corrected NU(+-DYN) in P P collisions for two values of midrapidity range.

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Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at sqrt(s)=0.9, 2.76 and 7 TeV

The ALICE collaboration Abelev, Betty ; Adam, Jaroslav ; Adamova, Dagmar ; et al.
Eur.Phys.J.C 72 (2012) 2124, 2012.
Inspire Record 1115186 DOI 10.17182/hepdata.58857

Measurements of the sphericity of primary charged particles in minimum bias proton--proton collisions at $\sqrt{s}=0.9$, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with $p_{\rm T}\geq0.5$ GeV/c in $|\eta|\leq0.8$. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity ($N_{\rm ch}$) is reported for events with different $p_{\rm T}$ scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low $N_{\rm ch}$, whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean $p_{\rm T}$ with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators.

7 data tables

pp @ 900 GeV, Mean Transverse Sphericity (y) vs Multiplicity.

pp @ 7000 GeV, Mean Transverse Sphericity (y) vs Multiplicity.

pp @ 2760 GeV, Mean Transverse Sphericity (y) vs Multiplicity.

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Underlying Event measurements in pp collisions at sqrt(s) = 0.9 and 7 TeV with the ALICE experiment at the LHC

The ALICE collaboration Abelev, Betty ; Abrahantes Quintana, Arian ; Adamova, Dagmar ; et al.
JHEP 07 (2012) 116, 2012.
Inspire Record 1080735 DOI 10.17182/hepdata.58863

We present measurements of Underlying Event observables in pp collisions at $\sqrt{s}$ = 0.9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum $p_{\rm T, LT}$ in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different $p_{\rm T}$ thresholds: 0.15, 0.5 and 1.0 GeV/$c$. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track $p){\rm T}$ threshold considered. Data are compared to Pythia 6.4, Pythia 8.1 and Phojet. On average, all models considered underestimate the multiplicity and summed $p_{\rm T}$ in the Transverse region by about 10-30%.

23 data tables

Number density as a function of the leading charged-particle PT at a centre-mass-energy of 900 GeV for events having charged-particle PT > 0.15 GeV. The data is shown for the three azimuthal regions.

Number density as a function of the leading charged-particle PT at a centre-mass-energy of 7000 GeV for events having charged-particle PT > 0.15 GeV. The data is shown for the three azimuthal regions.

Number density as a function of the leading charged-particle PT at a centre-mass-energy of 900 GeV for events having charged-particle PT > 0.5 GeV. The data is shown for the three azimuthal regions.

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Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV

The ALICE collaboration Aamodt, K. ; Abelev, B. ; Abrahantes Quintana, A. ; et al.
Phys.Rev.Lett. 108 (2012) 092301, 2012.
Inspire Record 930312 DOI 10.17182/hepdata.58113

The yield of charged particles associated with high-$p_{\rm T}$ trigger particles ($8 < p_{\rm T} < 15$ GeV/$c$) is measured with the ALICE detector in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jet-like correlation peaks in azimuthal di-hadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta $p_{\rm T}> 3$ GeV/$c$ on the away-side drops to about 60% of that observed in pp collisions, while on the near-side a moderate enhancement of 20-30% is found.

6 data tables

The ratio of near-side yields in Lead-Lead/Proton-Proton collisions in the central region.

The ratio of near-side yields in Lead-Lead/Proton-Proton collisions in the peripheral region.

The ratio of away-side yields in Lead-Lead/Proton-Proton collisions in the central region.

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Two-pion Bose-Einstein correlations in pp collisions at sqrt(s)=900 GeV

The ALICE collaboration Aamodt, K ; Abel, N ; Abeysekara, U. ; et al.
Phys.Rev.D 82 (2010) 052001, 2010.
Inspire Record 860477 DOI 10.17182/hepdata.55128

We report on the measurement of two-pion correlation functions from pp collisions at $\sqrt{s}=900$ GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the HBT radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at RHIC and at Tevatron, is not manifest in our data.

36 data tables

Two-particle correlation functions for like-sign and unlike sign pion pairs.

Two-particle correlation functions for like-sign and unlike sign pion pairs.

Two-particle correlation functions for like-sign and unlike sign pion pairs.

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First proton--proton collisions at the LHC as observed with the ALICE detector: measurement of the charged particle pseudorapidity density at sqrt(s) = 900 GeV

The ALICE collaboration Aamodt, K ; Abel, N ; Abeysekara, U ; et al.
Eur.Phys.J.C 65 (2010) 111-125, 2010.
Inspire Record 838352 DOI 10.17182/hepdata.53751

On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range |$\eta$| < 0.5, we obtain dNch/deta = 3.10 $\pm$ 0.13 (stat.) $\pm$ 0.22 (syst.) for all inelastic interactions, and dNch/deta = 3.51 $\pm$ 0.15 (stat.) $\pm$ 0.25 (syst.) for non-single diffractive interactions. These results are consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN SppS collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.

2 data tables

Pseudorapidity dependence of DN/DETARAP in Inelastic (INEL) and Non-Single-Diffractive (NSD) collisions. Note that the plot in the paper shows only statistical errors.

Pseudorapidity density for |ETARAP|<0.5 for Inelastic (INEL) and Non-Single-Diffractive (NSD) collisions.