Proton-Proton Interactions and Onset of Deconfinement

The NA61/SHINE collaboration Aduszkiewicz, A. ; Andronov, E.V. ; Anticic, T. ; et al.
Phys.Rev.C 102 (2020) 011901, 2020.
Inspire Record 1772241 DOI 10.17182/hepdata.95182

The NA61/SHINE experiment at the CERN SPS is performing a uniqe study of the phase diagram of strongly interacting matter by varying collision energy and nuclear mass number of colliding nuclei. In central Pb+Pb collisions the NA49 experiment found structures in the energy dependence of several observables in the CERN SPS energy range that had been predicted for the transition to a deconfined phase. New measurements of NA61/SHINE find intriguing similarities in p+p interactions for which no deconfinement transition is expected at SPS energies. Possible implications will be discussed.

12 data tables

K+/PI+ at y=0.

K+/PI+ at y=0.

<K+>/<PI+>.

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Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 2.76 and 5.02 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Eur.Phys.J.C 80 (2020) 534, 2020.
Inspire Record 1759853 DOI 10.17182/hepdata.88289

Anisotropies in the initial energy density distribution of the quark-gluon plasma created in high energy heavy ion collisions lead to anisotropies in the azimuthal distributions of the final-state particles known as collective flow. Fourier harmonic decomposition is used to quantify these anisotropies. The higher-order harmonics can be induced by the same order anisotropies (linear response) or by the combined influence of several lower order anisotropies (nonlinear response) in the initial state. The mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles are measured as functions of transverse momentum and centrality in PbPb collisions at nucleon-nucleon center-of-mass energies $\sqrt{s_\mathrm{NN}} =$ 2.76 and 5.02 TeV with the CMS detector. The results are compared with viscous hydrodynamic calculations using several different initial conditions, as well as microscopic transport model calculations. None of the models provides a simultaneous description of the mixed higher-order flow harmonics and nonlinear response coefficients.

90 data tables

Mixed higher-order flow harmonic $v_4\{\Psi_{22}\}$ from the scalar-product method at 5.02 TeV as a function of PT in the 0-20% centrality range.

Mixed higher-order flow harmonic $v_5\{\Psi_{23}\}$ from the scalar-product method at 5.02 TeV as a function of PT in the 0-20% centrality range.

Mixed higher-order flow harmonic $v_6\{\Psi_{222}\}$ from the scalar-product method at 5.02 TeV as a function of PT in the 0-20% centrality range.

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Version 2
Strange hadron production in pp and pPb collisions at $\sqrt{s_\mathrm{NN}}= $ 5.02 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Phys.Rev.C 101 (2020) 064906, 2020.
Inspire Record 1758692 DOI 10.17182/hepdata.88283

The transverse momentum ($p_\mathrm{T}$) distributions of $\Lambda$, $\Xi^-$, and $\Omega^-$ baryons, their antiparticles, and K$^0_\mathrm{S}$ mesons are measured in proton-proton (pp) and proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV over a broad rapidity range. The data, corresponding to integrated luminosities of 40.2 nb$^{-1}$ and 15.6 $\mu$b$^{-1}$ for pp and pPb collisions, respectively, were collected by the CMS experiment. The nuclear modification factor $R_\mathrm{pPb}$, defined as the ratio of the particle yield in pPb collisions and a scaled pp reference, is measured for each particle. A strong dependence on particle species is observed in the $p_\mathrm{T}$ range from 2 to 7 GeV, where $R_\mathrm{pPb}$ for K$^0_\mathrm{S}$ is consistent with unity, while an enhancement ordered by strangeness content and/or particle mass is observed for the three baryons. In pPb collisions, the strange hadron production is asymmetric about the nucleon-nucleon center-of-mass rapidity. Enhancements, which depend on the particle type, are observed in the direction of the Pb beam. The results are compared to predictions from EPOS LHC, which includes parametrized radial flow. The model is in qualitative agreement with the $R_\mathrm{pPb}$ data, but fails to describe the dependence on particle species in the yield asymmetries measured away from mid-rapidity in pPb collisions.

37 data tables

Invariant $p_{T}$-differential spectra of ${K_{0}}^{S}$ in p+p and p+Pb at $\sqrt{s}$=5.02 TeV in various |$y_{CM}$| ranges

Invariant $p_{T}$-differential spectra of ${K_{0}}^{S}$ in p+p and p+Pb at $\sqrt{s}$=5.02 TeV in various $y_{CM}$ ranges

Invariant $p_{T}$-differential spectra of $\Lambda + \bar{\Lambda}$ in p+p and p+Pb at $\sqrt{s}$=5.02 TeV in various |$y_{CM}$| ranges

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Measurement of $\phi $ meson production in $p + p$ interactions at 40, 80 and $158 \, \hbox {GeV}/c$ with the NA61/SHINE spectrometer at the CERN SPS

The NA61/SHINE collaboration Aduszkiewicz, A. ; Andronov, E.V. ; Antićić, T. ; et al.
Eur.Phys.J.C 80 (2020) 199, 2020.
Inspire Record 1749613 DOI 10.17182/hepdata.93228

Results on $\phi$ meson production in inelastic p+p collisions at CERN SPS energies are presented. They are derived from data collected by the NA61/SHINE fixed target experiment, by means of invariant mass spectra fits in the $\phi \to K^+K^-$ decay channel. They include the first ever measured double differential spectra of $\phi$ mesons as a function of rapidity $y$ and transverse momentum $p_T$ for proton beam momenta of 80 GeV/c and 158 GeV/c, as well as single differential spectra of $y$ or $p_T$ for beam momentum of 40 GeV/c. The corresponding total $\phi$ yields per inelastic p+p event are obtained. These results are compared with existing data on $\phi$ meson production in p+p collisions. The comparison shows consistency but superior accuracy of the present measurements. The emission of $\phi$ mesons in p+p reactions is confronted with that occurring in Pb+Pb collisions, and the experimental results are compared with model predictions. It appears that none of the considered models can properly describe all the experimental observables.

17 data tables

Double differential multiplicity of $\phi$ mesons produced in minimum bias p+p collisions at beam momentum of 158 GeV/c, as a function of transverse momentum $p_T$ and rapidity $y$.

Double differential multiplicity of $\phi$ mesons produced in minimum bias p+p collisions at beam momentum of 80 GeV/c, as a function of transverse momentum $p_T$ and rapidity $y$.

Transverse momentum $p_T$ spectrum of $\phi$ mesons produced in minimum bias p+p collisions at beam momentum of 40 GeV/c, in a broad rapidity $y$ bin of (0, 1.5).

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Charged-particle angular correlations in XeXe collisions at $\sqrt{s_{_\mathrm{NN}}}=$ 5.44 TeV

The CMS collaboration Sirunyan, Albert M ; Tumasyan, Armen ; Adam, Wolfgang ; et al.
Phys.Rev.C 100 (2019) 044902, 2019.
Inspire Record 1716441 DOI 10.17182/hepdata.88276

Azimuthal correlations of charged particles in xenon-xenon collisions at a center-of-mass energy per nucleon pair of $ \sqrt{s_{_\mathrm{NN}}} =$ 5.44 TeV are studied. The data were collected by the CMS experiment at the LHC with a total integrated luminosity of 3.42 $\mu$b$^{-1}$. The collective motion of the system formed in the collision is parameterized by a Fourier expansion of the azimuthal particle density distribution. The azimuthal anisotropy coefficients $v_{2}$, $v_{3}$, and $v_{4}$ are obtained by the scalar-product, two-particle correlation, and multiparticle correlation methods. Within a hydrodynamic picture, these methods have different sensitivities to non-collective and fluctuation effects. The dependence of the Fourier coefficients on the size of the colliding system is explored by comparing the xenon-xenon results with equivalent lead-lead data. Model calculations that include initial-state fluctuation effects are also compared to the experimental results. The observed angular correlations provide new constraints on the hydrodynamic description of heavy ion collisions.

24 data tables

Elliptic-flow coefficients $v_2$ based on the two-particle correlations technique, as functions of transverse momentum and in bins of centrality. The results correspond to the range $|\eta| < 2.4$.

Elliptic-flow coefficients $v_2$ based on the scalar-product technique, as functions of transverse momentum and in bins of centrality. The results correspond to the range $|\eta| < 0.8$.

Elliptic-flow coefficients $v_2$ based on the four-particle correlations technique, as functions of transverse momentum and in bins of centrality. The results correspond to the range $|\eta| < 2.4$.

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Collision Energy Dependence of Moments of Net-Kaon Multiplicity Distributions at RHIC

The STAR collaboration Adamczyk, L. ; Adams, J.R. ; Adkins, J.K. ; et al.
Phys.Lett.B 785 (2018) 551-560, 2018.
Inspire Record 1621460 DOI 10.17182/hepdata.98573

Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean ($M$), variance ($\sigma^2$), skewness ($S$), and kurtosis ($\kappa$) for net-kaon multiplicity distributions as well as the ratio $\sigma^2/M$ and the products $S\sigma$ and $\kappa\sigma^2$ are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.

43 data tables

Raw $\Delta N_k$ distributions in Au+Au collisions at 7.7 GeV for 0–5%, 30–40%, and 70–80% collision centralities at midrapidity. The distributions are not corrected for the finite centrality bin width effect nor the reconstruction efficiency.

Raw $\Delta N_k$ distributions in Au+Au collisions at 11.5 GeV for 0–5%, 30–40%, and 70–80% collision centralities at midrapidity. The distributions are not corrected for the finite centrality bin width effect nor the reconstruction efficiency.

Raw $\Delta N_k$ distributions in Au+Au collisions at 14.5 GeV for 0–5%, 30–40%, and 70–80% collision centralities at midrapidity. The distributions are not corrected for the finite centrality bin width effect nor the reconstruction efficiency.

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Beam Energy Dependence of Jet-Quenching Effects in Au+Au Collisions at $\sqrt{s_{_{ \mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV

The STAR collaboration Adamczyk, L. ; Adams, J.R. ; Adkins, J.K. ; et al.
Phys.Rev.Lett. 121 (2018) 032301, 2018.
Inspire Record 1609067 DOI 10.17182/hepdata.100537

We report measurements of the nuclear modification factor, $R_{ \mathrm{CP}}$, for charged hadrons as well as identified $\pi^{+(-)}$, $K^{+(-)}$, and $p(\overline{p})$ for Au+Au collision energies of $\sqrt{s_{_{ \mathrm{NN}}}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, and 62.4 GeV. We observe a clear high-$p_{\mathrm{T}}$ net suppression in central collisions at 62.4 GeV for charged hadrons which evolves smoothly to a large net enhancement at lower energies. This trend is driven by the evolution of the pion spectra, but is also very similar for the kaon spectra. While the magnitude of the proton $R_{ \mathrm{CP}}$ at high $p_{\mathrm{T}}$ does depend on collision energy, neither the proton nor the anti-proton $R_{ \mathrm{CP}}$ at high $p_{\mathrm{T}}$ exhibit net suppression at any energy. A study of how the binary collision scaled high-$p_{\mathrm{T}}$ yield evolves with centrality reveals a non-monotonic shape that is consistent with the idea that jet-quenching is increasing faster than the combined phenomena that lead to enhancement.

118 data tables

Charged hadron RCP for RHIC BES energies. The uncertainty bands at unity on the right side of the plot correspond to the pT-independent uncertainty in Ncoll scaling with the color in the band corresponding to the color of the data points for that energy. The vertical uncertainty bars correspond to statistical uncertainties and the boxes to systematic uncertainties.

Identified particle (Pion Plus) RCP for RHIC BES energies. The colored shaded boxes describe the point-to-point systematic uncertainties. The uncertainty bands at unity on the right side of the plot correspond to the pT -independent uncertainty in Ncoll scaling with the color in the band corresponding to the color of the data points for that energy.

Identified particle (Pion Minus) RCP for RHIC BES energies. The colored shaded boxes describe the point-to-point systematic uncertainties. The uncertainty bands at unity on the right side of the plot correspond to the pT -independent uncertainty in Ncoll scaling with the color in the band corresponding to the color of the data points for that energy.

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Measurements of $\pi^\pm$, K$^\pm$, p and $\bar{\textrm{p}}$ spectra in proton-proton interactions at 20, 31, 40, 80 and 158 GeV/c with the NA61/SHINE spectrometer at the CERN SPS

The NA61/SHINE collaboration Aduszkiewicz, A. ; Ali, Y. ; Andronov, E. ; et al.
Eur.Phys.J.C 77 (2017) 671, 2017.
Inspire Record 1598505 DOI 10.17182/hepdata.79533

Measurements of inclusive spectra and mean multiplicities of $\pi^\pm$, K$^\pm$, p and $\bar{\textrm{p}}$ produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($\sqrt{s} = $ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.

116 data tables

Transverse momentum-rapidity spectrum of K− produced in inelastic p+p interactions at 31 GeV/c with statistical uncertainties.

Transverse momentum-rapidity spectrum of K− produced in inelastic p+p interactions at 20 GeV/c with systematic uncertainties.

Transverse momentum-rapidity spectrum of K+ produced in inelastic p+p interactions at 20 GeV/c with statistical uncertainties.

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Bulk Properties of the Medium Produced in Relativistic Heavy-Ion Collisions from the Beam Energy Scan Program

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Phys.Rev.C 96 (2017) 044904, 2017.
Inspire Record 1510593 DOI 10.17182/hepdata.76977

We present measurements of bulk properties of the matter produced in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 19.6, 27, and 39 GeV using identified hadrons ($\pi^\pm$, $K^\pm$, $p$ and $\bar{p}$) from the STAR experiment in the Beam Energy Scan (BES) Program at the Relativistic Heavy Ion Collider (RHIC). Midrapidity ($|y|<$0.1) results for multiplicity densities $dN/dy$, average transverse momenta $\langle p_T \rangle$ and particle ratios are presented. The chemical and kinetic freeze-out dynamics at these energies are discussed and presented as a function of collision centrality and energy. These results constitute the systematic measurements of bulk properties of matter formed in heavy-ion collisions over a broad range of energy (or baryon chemical potential) at RHIC.

106 data tables

The average number of participating nucleons (⟨Npart⟩) for various collision centralities in Au+Au collisions at √sNN = 7.7–39 GeV.

Midrapidity (|y| < 0.1) transverse momentum spectra for (b) π- in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.

Midrapidity (|y| < 0.1) transverse momentum spectra for (a) π+ in Au+Au collisions at √sNN = 7.7 GeV for different centralities. The spectra for centralities other than 0–5% are scaled for clarity as shown in the figure. The curves represent the Bose-Einstein, mT -exponential, and double-exponential function fits to 0–5% central data for pions, kaons, and (anti)protons, respectively. The uncertainties are statistical and systematic added in quadrature.

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Version 2
Global $\Lambda$ hyperon polarization in nuclear collisions: evidence for the most vortical fluid

The STAR collaboration Adamczyk, L. ; Adkins, J.K. ; Agakishiev, G. ; et al.
Nature 548 (2017) 62-65, 2017.
Inspire Record 1510474 DOI 10.17182/hepdata.77494

The extreme temperatures and energy densities generated by ultra-relativistic collisions between heavy nuclei produce a state of matter with surprising fluid properties. Non-central collisions have angular momentum on the order of 1000$\hbar$, and the resulting fluid may have a strong vortical structure that must be understood to properly describe the fluid. It is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have so far been found. Here we present the first measurement of an alignment between the angular momentum of a non-central collision and the spin of emitted particles, revealing that the fluid produced in heavy ion collisions is by far the most vortical system ever observed. We find that $\Lambda$ and $\overline{\Lambda}$ hyperons show a positive polarization of the order of a few percent, consistent with some hydrodynamic predictions. A previous measurement that reported a null result at higher collision energies is seen to be consistent with the trend of our new observations, though with larger statistical uncertainties. These data provide the first experimental access to the vortical structure of the "perfect fluid" created in a heavy ion collision. They should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the Strong Force. Our results extend the recent discovery of hydrodynamic spin alignment to the subatomic realm.

2 data tables

Lambda and AntiLambda polarization as a function of collision energy. A 0.8% error on the alpha value used in the paper is corrected in this table. Systematic error bars include those associated with particle identification (negligible), uncertainty in the value of the hyperon decay parameter (2%) and reaction plane resolution (2%) and detector efficiency corrections (4%). The dominant systematic error comes from statistical fluctuations of the estimated combinatoric background under the (anti-)$\Lambda$ mass peak.

Lambda and AntiLambda polarization as a function of collision energy calculated using the new $\alpha_\Lambda=0.732$ updated on PDG2020. Systematic error bars include those associated with particle identification (negligible), uncertainty in the value of the hyperon decay parameter (2%) and reaction plane resolution (2%) and detector efficiency corrections (4%). The dominant systematic error comes from statistical fluctuations of the estimated combinatoric background under the (anti-)$\Lambda$ mass peak.