Transverse single-spin asymmetries of midrapidity $\pi^0$ and $\eta$ mesons in polarized $p+p$ collisions at $\sqrt{s}=200$ GeV

The PHENIX collaboration Acharya, U.A. ; Aidala, C. ; Akiba, Y. ; et al.
Phys.Rev.D 103 (2021) 052009, 2021.
Inspire Record 1833997 DOI 10.17182/hepdata.105043

We present a measurement of the transverse single-spin asymmetry for $\pi^0$ and $\eta$ mesons in $p^\uparrow$$+$$p$ collisions in the pseudorapidity range $|\eta|<0.35$ and at a center-of-mass energy of 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. In comparison with previous measurements in this kinematic region, these results have a factor of 3 smaller uncertainties. As hadrons, $\pi^0$ and $\eta$ mesons are sensitive to both initial- and final-state nonperturbative effects for a mix of parton flavors. Comparisons of the differences in their transverse single-spin asymmetries have the potential to disentangle the possible effects of strangeness, isospin, or mass. These results can constrain the twist-3 trigluon collinear correlation function as well as the gluon Sivers function.

2 data tables

Data from Figs. 2, 4, and 5 of the transverse single-spin asymmetry of neutral pions measured at $|\eta|<0.35$ in $p^\uparrow$$+$$p$ collisions at $\sqrt{s} = 200$ GeV. An additional scale uncertainty of 3.4\% due to the polarization uncertainty is not shown. The total $\sigma_{\rm syst}$ in the lowest $p_T$ bin includes an additional systematic uncertainty of $1.06\times10^{-4}$ from bunch shuffling.

Data from Figs. 3 and 4 of the transverse single-spin asymmetry of eta mesons measured at $|\eta|<0.35$ in $p^\uparrow$$+$$p$ collisions at $\sqrt{s} = 200$ GeV. An additional scale uncertainty of 3.4\% due to the polarization uncertainty is not shown. The total $\sigma_{\rm syst}$ in the lowest $p_T$ bin includes an additional systematic uncertainty of $6.20\times10^{-4}$ from bunch shuffling.


Measurement of jet-medium interactions via direct photon-hadron correlations in Au$+$Au and $d$ $+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Acharya, U. ; Adare, A. ; Afanasiev, S. ; et al.
Phys.Rev.C 102 (2020) 054910, 2020.
Inspire Record 1798493 DOI 10.17182/hepdata.101752

We present direct photon-hadron correlations in 200 GeV/A Au+Au, d+Au, and p+p collisions, for direct photon pT from 5–12 GeV/c, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in d+Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au+Au compared to p+p and d+Au. As the momentum fraction decreases, the yield of hadrons in Au+Au increases to an excess over the yield in p+p collisions. The excess is at large angles and at low hadron pT and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.

14 data tables

Per-trigger yield of hadrons associated to direct photons in Au+Au collisions for direct photon $p_T$ 5-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.

Per-trigger yield of hadrons associated to direct photons in d+Au collisions for direct photon $p_T$ 7-9 GeV/$c$, compared with p+p baseline, in various $\xi$ bins.

Integrated away-side $\gamma_{dir}$-h per-trigger yields of Au+Au, d+Au, and p+p, as a function of $\xi$.

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Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized $p+p$ collisions at $\sqrt {s}$ = 510 GeV

The PHENIX collaboration Acharya, U.A. ; Adare, A. ; Aidala, C. ; et al.
Phys.Rev.D 102 (2020) 032001, 2020.
Inspire Record 1789851 DOI 10.17182/hepdata.95883

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, $A_{LL}$, for charged pions at midrapidity ($|\eta|<0.35$) in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510$ GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction $x$ range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at $\sqrt{s}=200$ GeV, which show a nonzero positive contribution of gluon spin to the proton spin.

1 data table

Double-spin asymmetries $A_{LL}$ as a function of transverse momentum for positive and negative pions.


Measurement of $J/\psi$ at forward and backward rapidity in $p+p$, $p+A$l, $p+A$u, and $^3$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200~{\rm GeV}$

The PHENIX collaboration Acharya, U. ; Adare, A. ; Aidala, C. ; et al.
Phys.Rev.C 102 (2020) 014902, 2020.
Inspire Record 1762446 DOI 10.17182/hepdata.98626

Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of charmonium in small systems have become increasingly relevant. We present the results of J/ψ measurements at forward and backward rapidity in various small collision systems, p+p, p+Al, p+Au and 3He+Au, at √sNN =200 GeV. The results are presented in the form of the observable RAB, the nuclear modification factor, a measure of the ratio of the J/ψ invariant yield compared to the scaled yield in p+p collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on J/ψ production with different projectile sizes p and 3He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for p+Au and 3He+Au. However, for 0%–20% central collisions at backward rapidity, the modification for 3He+Au is found to be smaller than that for p+Au, with a mean fit to the ratio of 0.89±0.03(stat)±0.08(syst), possibly indicating final state effects due to the larger projectile size.

36 data tables

J/psi invariant yields in p+p collisions as a function of pT at forward and backward rapidity. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.

J/psi nuclear modification in p+Al, p+Au and 3He+Au collisions as a function of centrality and rapidity. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.

J/psi nuclear modification in p+Al collisions as a function of centrality and rapidity. The statistical and systematic uncertainties vary point-to-point and are listed for each measured value. An additional global systematic uncertainty is provided in each column heading, which applies to all data points per column.

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Production of $\pi^0$ and $\eta$ mesons in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV

The PHENIX collaboration Aidala, C. ; Ajitanand, N.N. ; Akiba, Y. ; et al.
Phys.Rev.C 98 (2018) 054903, 2018.
Inspire Record 1672859 DOI 10.17182/hepdata.100192

Production of $\pi^0$ and $\eta$ mesons has been measured at midrapidity in Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV. Measurements were performed in $\pi^0(\eta)\rightarrow\gamma\gamma$ decay channel in the 1(2)-20 GeV/$c$ transverse momentum range. A strong suppression is observed for $\pi^0$ and $\eta$ meson production at high transverse momentum in central Cu$+$Au collisions relative to the $p$$+$$p$ results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au$+$Au with comparable nuclear overlap. The $\eta/\pi^0$ ratio measured as a function of transverse momentum is consistent with $m_T$-scaling parameterization down to $p_T=$2 GeV/$c$, its asymptotic value is constant and consistent with Au$+$Au and $p$$+$$p$ and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in $e^+e^-$ collisions in a range of collision energies $\sqrt{s_{_{NN}}}=$3--1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu$+$Cu collisions either does not affect the jet fragmentation into light mesons or it affects the $\pi^0$ and $\eta$ the same way.

48 data tables

$\pi^0$ spectra from figure 3a from minimum bias Cu+Au collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.

$\pi^0$ spectra from figure 3a from 0-10% central Cu+Au collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.

$\pi^0$ spectra from figure 3a from 10-20% central Cu+Au collisions. Type A uncertainties are uncorrelated point-to-point. Type B uncertainties are correlated point-to-point. Type C uncertainties affect the scale of the data.

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Creation of quark–gluon plasma droplets with three distinct geometries

The PHENIX collaboration Aidala, C. ; Akiba, Y. ; Alfred, M. ; et al.
Nature Phys. 15 (2019) 214-220, 2019.
Inspire Record 1672133 DOI 10.17182/hepdata.99787

The experimental study of the collisions of heavy nuclei at relativistic energies has established the properties of the quark-gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons. In this state, matter behaves as a nearly inviscid fluid that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the produced particles, producing a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton-proton ($p$$+$$p$) and proton-nucleus ($p$$+$$A$) collisions, despite expectations that the volume and lifetime of the medium produced would be too small to form a QGP. Here, we report on the observation of elliptic and triangular flow patterns of charged particles produced in proton-gold ($p$$+$Au), deuteron-gold ($d$$+$Au), and helium-gold ($^3$He$+$Au) collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_{_{NN}}}$~=~200 GeV. The unique combination of three distinct initial geometries and two flow patterns provides unprecedented model discrimination. Hydrodynamical models, which include the formation of a short-lived QGP droplet, provide a simultaneous description of these measurements.

16 data tables

$v_2$for 0-5% central p+Au collisions

$v_2$for 0-5% central d+Au collisions

$v_2$for 0-5% central $^3$He+Au collisions

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Study of the process $e^+e^-\to\omega\eta\pi^0$ in the energy range $\sqrt{s} <2$ GeV with the SND detector

Achasov, M.N. ; Aulchenko, V.M. ; Barnyakov, A.Yu. ; et al.
Phys.Rev.D 94 (2016) 032010, 2016.
Inspire Record 1471515 DOI 10.17182/hepdata.82577

The process $e^+e^-\to\omega\eta\pi^0$ is studied in the energy range $1.45-2.00$ GeV using data with an integrated luminosity of 33 pb$^{-1}$ accumulated by the SND detector at the $e^+e^-$ collider VEPP-2000. The $e^+e^-\to\omega\eta\pi^0$ cross section is measured for the first time. The cross section has a threshold near 1.75 GeV. Its value is about 2 nb in the energy range $1.8-2.0$ GeV. The dominant intermediate state for the process $e^+e^- \to \omega\eta\pi^0$ is found to be $\omega a_0(980)$.

1 data table

The energy interval, integrated luminosity ($L$), number of selected events ($N$), estimated number of background events ($N_{bkg}$), detection efficiency for $e^+e^-\to\omega\eta\pi^0\to 7\gamma$ events ($\epsilon$), radiative correction ($\delta+1$), and $e^+e^-\to\omega\eta\pi^0$ Born cross section ($\sigma$). The shown cross-section errors are statistical. The systematic error is 4.2%. The 90% confidence level upper limits are listed for the first two energy intervals.


Study of the process $e^+ e^- \to K^0_{S}K^0_{L}$ in the center-of-mass energy range 1004--1060 MeV with the CMD-3 detector at the VEPP-2000 $e^+ e^-$ collider

The CMD-3 collaboration Kozyrev, E.A. ; Solodov, E.P. ; Amirkhanov, A.N. ; et al.
Phys.Lett.B 760 (2016) 314-319, 2016.
Inspire Record 1444990 DOI 10.17182/hepdata.78538

The $e^+ e^- \to K^0_{S}K^0_{L}$ cross section has been measured in the center-of-mass energy range 1004--1060 MeV at 25 energy points using $6.1 \times 10^5$ events with $K^0_{S}\to \pi^+\pi^-$ decay. The analysis is based on 5.9 pb$^{-1}$ of an integrated luminosity collected with the CMD-3 detector at the VEPP-2000 $e^+ e^-$ collider. To obtain $\phi(1020)$ meson parameters the measured cross section is approximated according to the Vector Meson Dominance model as a sum of the $\rho, \omega, \phi$-like amplitudes and their excitations. This is the most precise measurement of the $e^+ e^- \to K^0_{S}K^0_{L}$ cross section with a 1.8\% systematic uncertainty.

1 data table

The c.m. energy $E_{\rm c.m.}$, number of selected signal events $N$, detection efficiency $\epsilon_{\rm MC}$, radiative-correction factor 1 + $\delta_{\rm rad.}$, integrated luminosity $L$, and Born cross section $\sigma$ of the process $e^+ e^- \to K^0_{S}K^0_{L}$.


Study of the reaction $e^+e^- \to \pi^0\gamma$ with the SND detector at the VEPP-2M collider

The SND collaboration Achasov, M.N. ; Beloborodov, K.I. ; Berdyugin, A.V. ; et al.
Phys.Rev.D 93 (2016) 092001, 2016.
Inspire Record 1418483 DOI 10.17182/hepdata.77047

The process $e^+e^- \to \pi^0\gamma$ has been studied in the experiment with the SND detector at the VEPP-2M $e^+e^-$ collider. The $e^+e^- \to \pi^0\gamma$ cross section has been measured in the center-of-mass energy range from 0.60 to 1.38 GeV. The cross section is well described by the vector meson dominance model. From the fit to the cross section data we have determined the branching fractions $B(\rho\to\pi^0\gamma)=(4.20\pm0.52)\times10^{-4}$, $B(\omega\to\pi^0\gamma)=(8.88\pm0.18)\%$, $B(\phi\to\pi^0\gamma)=(1.367\pm0.072)\times10^{-3}$, and the relative phase between the $\rho$ and $\omega$ amplitudes $\varphi_{\rho}=(-12.7\pm4.5)^\circ$. Our data on the process $e^+e^- \to \pi^0\gamma$ are the most accurate to date.

1 data table

The c.m.energy ($E$), integrated luminosity ($L$), detection efficiency ($\varepsilon$), number of selected signal events ($N_{\rm sig}$), radiative-correction factor ($1+\delta$), measured Born cross section ($\sigma$). For the cross section the first error is statistical, the second is systematic.


Inclusive production of pions by protons in nuclei at low energies

Guber, F.F. ; Kazarnovskii, M.V. ; Krasnov, V.A. ; et al.
JETP Lett. 31 (1980) 656, 1980.
Inspire Record 1408595 DOI 10.17182/hepdata.70448
3 data tables

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