Rapidity Dependence of Charged Antiparticle-to-Particle Ratios in Au+Au Collisions at $\sqrt{s_{NN}}=200$ GeV

The BRAHMS collaboration Bearden, I.G. ; Beavis, D. ; Besliu, C. ; et al.
Phys.Rev.Lett. 90 (2003) 102301, 2003.
Inspire Record 590481 DOI 10.17182/hepdata.110251

We present ratios of the numbers of charged antiparticles to particles (pions, kaons and protons) in Au + Au collisions at $\sqrt{s_{NN}}=200$ GeV as a function of rapidity in the range $y$=0-3. While the particle ratios at midrapidity are approaching unity, the $K^-/K^+$ and $\bar{p}/p$ ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from $\mu_B \approx 130$MeV at $y$=3 to $\mu_B \approx 25$MeV at $y$=0.

0 data tables match query

Rapidity dependence of antiproton to proton ratios in Au + Au collisions at s(NN)**(1/2) = 130-GeV.

The BRAHMS collaboration Bearden, I.G. ; Beavis, D. ; Besliu, C. ; et al.
Phys.Rev.Lett. 87 (2001) 112305, 2001.
Inspire Record 558361 DOI 10.17182/hepdata.110347

Measurements, with the BRAHMS detector, of the antiproton to proton ratio at central and forward rapidities are presented for Au+Au reactions at sqrt{s_{NN}}=130 GeV, and for three different collision centralities. For collisions in the 0-40% centrality range we find $N(\bar{{\rm p}})/N({\rm p}) = 0.64 +- 0.04 (stat.) +- 0.06 (syst.) at y ~0, 0.66 +- 0.03 +- 0.06 at y ~ 0.7, and 0.41 +- 0.04 +- 0.06 at y ~ 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The measurements demonstrate that the antiproton and proton rapidity densities vary differently with rapidity, and indicate that a net-baryon free midrapidity plateau (Bjorken limit) is not reached at this RHIC energy.

0 data tables match query

Rapidity and centrality dependence of particle production for identified hadrons in Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV

The BRAHMS collaboration Arsene, I.C. ; Bearden, I.G. ; Beavis, D. ; et al.
Phys.Rev.C 94 (2016) 014907, 2016.
Inspire Record 1419279 DOI 10.17182/hepdata.89453

The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at $\sqrt{s_{NN}} = 200$ GeV. As the collisions become more central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled $p+p$ collisions. This suppression, which increases as the collisions become more central is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. The ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.

0 data tables match query

Rapidity dependence of the proton-to-pion ratio in Au+Au and p+p collisions at sqrt(s_NN) = 62.4 and 200 GeV

The BRAHMS collaboration Arsene, I.G. ; Bearden, I.G. ; Beavis, D. ; et al.
Phys.Lett.B 684 (2010) 22-27, 2010.
Inspire Record 834310 DOI 10.17182/hepdata.89450

The proton-to-pion ratios measured in the BRAHMS experiment for Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 62.4 and 200 GeV are presented as a function of transverse momentum and collision centrality at selected pseudorapidities in the range of 0 to 3.8. A strong pseudorapidity dependence of these ratios is observed. We also compare the magnitude and p_T-dependence of the p/pi ratios measured in Au+Au collisions at \rootsnn{200} and $\eta \approx 2.2$ with the same ratio measured at \rootsnn{62.4} and $\eta = 0$. The great similarity found between these ratios throughout the whole p_T range (up to 2.2 GeV/$c$) is consistent with particle ratios in A+A collisions being described with grand-canonical distributions characterized by the baryo-chemical potential \mibn. At the collision energy of 62.4 GeV, we have observed a unique point in pseudorapidity, $\eta = 3.2$, where the p/pi+ ratio is independent of the collision system size in a wide p_T-range of $0.3 \le p_{T} \le 1.8$ GeV/$c$.

0 data tables match query

$\psi(2S)$ suppression in Pb-Pb collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Rev.Lett. 132 (2024) 042301, 2024.
Inspire Record 2165947 DOI 10.17182/hepdata.145654

The production of the $\psi(2S)$ charmonium state was measured with ALICE in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ($2.5<y<4$). The measurement of the ratio of the inclusive production cross sections of the $\psi(2S)$ and J/$\psi$ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region $p_{\rm T}<12$ GeV/$c$. The results are compared with the corresponding measurements in pp collisions, by forming the double ratio $[\sigma^{\psi(2S)}/\sigma^{J/\psi}]_{\rm{Pb-Pb}}/[\sigma^{\psi(2S)}/\sigma^{J/\psi}]_{\rm{pp}}$. It is found that in Pb-Pb collisions the $\psi(2S)$ is suppressed by a factor of $\sim 2$ with respect to the J/$\psi$. The $\psi(2S)$ nuclear modification factor $R_{\rm AA}$ was also obtained as a function of both centrality and $p_{\rm T}$. The results show that the $\psi(2S)$ resonance yield is strongly suppressed in Pb-Pb collisions, by a factor up to $\sim 3$ with respect to pp. Comparisons of cross section ratios with previous SPS findings by the NA50 experiment and of $R_{\rm AA}$ with higher-$p_{\rm T}$ results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.

0 data tables match query

D-meson production in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV and in pp collisions at $\sqrt{s}=7$ TeV

The ALICE collaboration Adam, Jaroslav ; Adamova, Dagmar ; Aggarwal, Madan Mohan ; et al.
Phys.Rev.C 94 (2016) 054908, 2016.
Inspire Record 1465513 DOI 10.17182/hepdata.73941

The production cross sections of the prompt charmed mesons D$^0$, D$^+$, D$^{*+}$ and D$_s$ were measured at mid-rapidity in p-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV with the ALICE detector at the LHC. D mesons were reconstructed from their decays D$^0\rightarrow{\rm K}^-\pi^+$, D$^+\rightarrow{\rm K}^-\pi^+\pi^+$, D$^{*+}\rightarrow D^0\pi^+$, D$_s^+\rightarrow\phi\pi^+\rightarrow{\rm K}^-{\rm K}^+\pi^+$, and their charge conjugates. The $p_{\rm T}$-differential production cross sections were measured at mid-rapidity in the interval $1<p_{\rm T}<24$ GeV/$c$ for D$^0$, D$^+$ and D$^{*+}$ mesons and in $2<p_{\rm T}<12$ GeV/$c$ for D$_s$ mesons, using an analysis method based on the selection of decay topologies displaced from the interaction vertex. The production cross sections of the D$^0$, D$^+$ and D$^{*+}$ mesons were also measured in three $p_{\rm T}$ intervals as a function of the rapidity $y_{\rm cms}$ in the centre-of-mass system in $-1.26<y_{\rm cms}<0.34$. In addition, the prompt D$^0$ cross section was measured in pp collisions at $\sqrt{s}=7$ TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV down to $p_{\rm T}=0$ using an analysis technique that is based on the estimation and subtraction of the combinatorial background, without reconstruction of the D$^0$ decay vertex. The nuclear modification factor $R_{\rm pPb}(p_{\rm T})$, defined as the ratio of the $p_{\rm T}$-differential D-meson cross section in p-Pb collisions and that in pp collisions scaled by the mass number of the Pb nucleus, was calculated for the four D-meson species and found to be compatible with unity within experimental uncertainties. The results are compared to theoretical calculations that include cold-nuclear-matter effects and to transport model calculations incorporating the interactions of charm quarks with an expanding deconfined medium.

0 data tables match query

W$^\pm$-boson production in p$-$Pb collisions at $\sqrt{s_{NN}} = 8.16$ TeV and PbPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 05 (2023) 036, 2023.
Inspire Record 2071184 DOI 10.17182/hepdata.133034

The production of the W$^\pm$ bosons measured in p$-$Pb collisions at a centre-of-mass energy per nucleon$-$nucleon collision $\sqrt{s_{NN}} = 8.16$ TeV and Pb$-$Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV with ALICE at the LHC is presented. The W$^\pm$ bosons are measured via their muonic decay channel, with the muon reconstructed in the pseudorapidity region $-4 < \eta^\mu_{\rm lab} < -2.5$ with transverse momentum $p_{\rm T}^\mu > 10$ GeV/$c$. While in Pb$-$Pb collisions the measurements are performed in the forward ($2.5 < y^\mu_{\rm cms} < 4$) rapidity region, in p$-$Pb collisions, where the centre-of-mass frame is boosted with respect to the laboratory frame, the measurements are performed in the backward ($-4.46 < y^\mu_{\rm cms} < -2.96$) and forward ($2.03 < y^\mu_{\rm cms} < 3.53$) rapidity regions. The W$^{-}$ and W$^{+}$ production cross sections, lepton-charge asymmetry, and nuclear modification factors are evaluated as a function of the muon rapidity. In order to study the production as a function of the p$-$Pb collision centrality, the production cross sections of the W$^{-}$ and W$^{+}$ bosons are combined and normalised to the average number of binary nucleon$-$nucleon collision $\langle N_\mathrm{coll} \rangle$. In Pb$-$Pb collisions, the same measurements are presented as a function of the collision centrality. Study of the binary scaling of the W$^\pm$-boson cross sections in p$-$Pb and Pb$-$Pb collisions is also reported. The results are compared with perturbative QCD (pQCD) calculations, with and without nuclear modifications of the Parton Distribution Functions (PDFs), as well as with available data at the LHC. Significant deviations from the theory expectations are found in the two collision systems, indicating that the measurements can provide additional constraints for the determination of nuclear PDF (nPDFs) and in particular of the light-quark distributions.

0 data tables match query

J/psi polarization in pp collisions at sqrt(s)=7 TeV

The ALICE collaboration Abelev, Betty ; Abrahantes Quintana, Arian ; Adamova, Dagmar ; et al.
Phys.Rev.Lett. 108 (2012) 082001, 2012.
Inspire Record 944730 DOI 10.17182/hepdata.73005

We have studied J/psi production in pp collisions at $\sqrt{s}=7$ TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/$\psi$ polarization parameters $\lambda_{\theta}$ and $\lambda_\phi$ were obtained. The study was performed in the kinematic region 2.5<y<4, 2<$p_{\rm T}$<8 GeV/$c$, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.

0 data tables match query

Underlying Event properties in pp collisions at $\sqrt{s}$ = 13 TeV

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
JHEP 04 (2020) 192, 2020.
Inspire Record 1762350 DOI 10.17182/hepdata.94414

This article reports measurements characterizing the Underlying Event (UE) associated with hard scatterings at midrapidity in pp collisions at $\sqrt{s}=13$ TeV. The hard scatterings are identified by the leading particle, the charged particle with the highest transverse momentum ($p_{\rm T}^{\rm leading}$) in the event. Charged-particle number and summed transverse-momentum densities are measured in different azimuthal regions defined with respect to the leading particle direction: Toward, Transverse, and Away. The Toward and Away regions contain the fragmentation products of the hard scatterings in addition to the UE contribution, whereas particles in the Transverse region are expected to originate predominantly from the UE. The study is performed as a function of $p_{\rm T}^{\rm leading}$ with three different $p_{\rm T}$ thresholds for the associated particles, $p_{\rm T}^{\rm min} >$ 0.15, 0.5, and 1.0 GeV/$c$. The charged-particle density in the Transverse region rises steeply for low values of $p_{\rm T}^{\rm leading}$ and reaches a plateau. The results confirm the trend that the charged-particle density in the Transverse region shows a stronger increase with $\sqrt{s}$ than the inclusive charged-particle density at midrapidity. The UE activity is increased by approximately 20% when going from 7 to 13 TeV. The plateau in the Transverse region ($5 < p_{\rm T}^{\rm leading} < ~ 40$ GeV/$c$ ) is further characterized by the probability distribution of its charged-particle multiplicity normalized to its average value (relative transverse activity, $R_{T}$) and the mean transverse momentum as a function of $R_{T}$. Experimental results are compared to model calculations using PYTHIA 8 and EPOS LHC. The overall agreement between models and data is within 30%. These measurements provide new insights on the interplay between hard scatterings and the associated UE in pp collisions.

0 data tables match query

First measurement of quarkonium polarization in nuclear collisions at the LHC

The ALICE collaboration Acharya, Shreyasi ; Adamova, Dagmar ; Adler, Alexander ; et al.
Phys.Lett.B 815 (2021) 136146, 2021.
Inspire Record 1797469 DOI 10.17182/hepdata.102403

The polarization of inclusive J/$\psi$ and $\Upsilon(1{\rm S})$ produced in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region $2.5<y<4$ and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters $\lambda_{\theta}$, $\lambda_{\phi}$ and $\lambda_{\theta\phi}$ are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval $2<p_{\rm T}<10$ GeV/$c$ and $p_{\rm T}<15$ GeV/$c$ for the J/$\psi$ and $\Upsilon(1{\rm S})$, respectively. The polarization parameters for the J/$\psi$ are found to be compatible with zero, within a maximum of about two standard deviations at low $p_{\rm T}$, for both reference frames and over the whole $p_{\rm T}$ range. The values are compared with the corresponding results obtained for pp collisions at $\sqrt{s}=7$ and 8 TeV in a similar kinematic region by the ALICE and LHCb experiments. Although with much larger uncertainties, the polarization parameters for $\Upsilon(1{\rm S})$ production in Pb-Pb collisions are also consistent with zero.

0 data tables match query