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Measurement of Spin-Density Matrix Elements in $\rho(770)$ Production with a Linearly Polarized Photon Beam at $E_\gamma = 8.2\,-\,8.8\,\text{GeV}$

The GlueX collaboration Adhikari, S. ; Afzal, F. ; Akondi, C.S. ; et al.
Phys.Rev.C 108 (2023) 055204, 2023.
Inspire Record 2660186 DOI 10.17182/hepdata.140672

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized $8.5\,\text{GeV}$ photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson $\rho$(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of $s$-channel helicity conservation at small squared four-momentum transfer $t$ and are able to extract the $t$-dependence of natural and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full $t$ range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced $\rho(770)$ differ by two units are negligible for $-t<0.5\,\text{GeV}^{2}/c^{2}$.

2 data tables

Spin-density matrix elements for the photoproduction of $\rho(770)$ in the helicity system. The first uncertainty is statistical, the second systematic. The systematic uncertainties for the polarized SDMEs $\rho^1_{ij}$ and $\rho^2_{ij}$ contain an overall relative normalization uncertainty of 2.1% which is fully correlated for all values of $-t$.

Spin-density matrix elements for the photoproduction of $\rho(770)$ in the helicity system. The first uncertainty is statistical, the second systematic. The systematic uncertainties for the polarized SDMEs $\rho^1_{ij}$ and $\rho^2_{ij}$ contain an overall relative normalization uncertainty of 2.1% which is fully correlated for all values of $-t$.


Measurement of the J/$\psi $ photoproduction cross section over the full near-threshold kinematic region

The GlueX collaboration Adhikari, S. ; Afzal, F. ; Akondi, C.S. ; et al.
Phys.Rev.C 108 (2023) 025201, 2023.
Inspire Record 2649988 DOI 10.17182/hepdata.140802

We report the total and differential cross sections for $J/\psi$ photoproduction with the large acceptance GlueX spectrometer for photon beam energies from the threshold at 8.2~GeV up to 11.44~GeV and over the full kinematic range of momentum transfer squared, $t$. Such coverage facilitates the extrapolation of the differential cross sections to the forward ($t = 0$) point beyond the physical region. The forward cross section is used by many theoretical models and plays an important role in understanding $J/\psi$ photoproduction and its relation to the $J/\psi-$proton interaction. These measurements of $J/\psi$ photoproduction near threshold are also crucial inputs to theoretical models that are used to study important aspects of the gluon structure of the proton, such as the gluon Generalized Parton Distribution (GPD) of the proton, the mass radius of the proton, and the trace anomaly contribution to the proton mass. We observe possible structures in the total cross section energy dependence and find evidence for contributions beyond gluon exchange in the differential cross section close to threshold, both of which are consistent with contributions from open-charm intermediate states.

4 data tables

$\gamma p \rightarrow J/\psi p$ total cross sections in bins of beam energy. The first uncertainties are statistical, and the second are systematic. There is an additional fully correlated systematic uncertainty of 19.5% on the total cross section, not included here.

$\gamma p \rightarrow J/\psi p$ differential cross sections 8.2–9.28 GeV beam energy range, average $t$ and beam energy in bins of $t$. The first cross section uncertainties are statistical, and the second are systematic. The overall average beam energy is 8.93 GeV. There is an additional fully correlated systematic uncertainty of 19.5% on the total cross section, not included here.

$\gamma p \rightarrow J/\psi p$ differential cross sections 9.28–10.36 GeV beam energy range, average $t$ and beam energy in bins of $t$. The first cross section uncertainties are statistical, and the second are systematic. The overall average beam energy is 9.86 GeV. There is an additional fully correlated systematic uncertainty of 19.5% on the total cross section, not included here.

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Transverse single-spin asymmetry of midrapidity $\pi^{0}$ and $\eta$ mesons in $p$+Au and $p$+Al collisions at $\sqrt{s_{_{NN}}}=$ 200 GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Aidala, C. ; et al.
Phys.Rev.D 107 (2023) 112004, 2023.
Inspire Record 2641468 DOI 10.17182/hepdata.139098

Presented are the first measurements of the transverse single-spin asymmetries ($A_N$) for neutral pions and eta mesons in $p$+Au and $p$+Al collisions at $\sqrt{s_{_{NN}}}=200$ GeV in the pseudorapidity range $|\eta|<$0.35 with the PHENIX detector at the Relativistic Heavy Ion Collider. The asymmetries are consistent with zero, similar to those for midrapidity neutral pions and eta mesons produced in $p$+$p$ collisions. These measurements show no evidence of additional effects that could potentially arise from the more complex partonic environment present in proton-nucleus collisions.

2 data tables

Data from Figure 2 (a) of the $\pi^{0}$ transverse single-spin asymmetry in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow}+$Au and $p^{\uparrow}+$Al collisions as a function of $p_{T}$.

Data from Figure 2 (b) of the $\eta$ transverse single-spin asymmetry in $\sqrt{s_{NN}}=200$ GeV $p^{\uparrow}+$Au and $p^{\uparrow}+$Al collisions as a function of $p_{T}$.


Measurement of $\phi$-meson production in Cu$+$Au at $\sqrt{s_{_{NN}}}=200$ GeV and U$+$U at $\sqrt{s_{_{NN}}}=193$ GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Aidala, C. ; et al.
Phys.Rev.C 107 (2023) 014907, 2023.
Inspire Record 2623245 DOI 10.17182/hepdata.132483

The PHENIX experiment reports systematic measurements at the Relativistic Heavy Ion Collider of $\phi$-meson production in asymmetric Cu$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV and in U$+$U collisions at $\sqrt{s_{_{NN}}}$=193 GeV. Measurements were performed via the $\phi\rightarrow K^{+}K^{-}$ decay channel at midrapidity $|\eta|<0.35$. Features of $\phi$-meson production measured in Cu$+$Cu, Cu$+$Au, Au$+$Au, and U$+$U collisions were found to not depend on the collision geometry, which was expected because the yields are averaged over the azimuthal angle and follow the expected scaling with nuclear-overlap size. The elliptic flow of the $\phi$ meson in Cu$+$Au, Au$+$Au, and U$+$U collisions scales with second-order-participant eccentricity and the length scale of the nuclear-overlap region (estimated with the number of participating nucleons). At moderate $p_T$, $\phi$-meson production measured in Cu$+$Au and U$+$U collisions is consistent with coalescence-model predictions, whereas at high $p_T$ the production is in agreement with expectations for in-medium energy loss of parent partons prior to their fragmentation. The elliptic flow for $\phi$ mesons measured in Cu$+$Au and U$+$U collisions is well described by a (2+1)D viscous-hydrodynamic model with specific-shear viscosity $\eta/s=1/4\pi$.

14 data tables

Invariant transverse momentum spectra measured for $\phi$ mesons in (a) Cu+Au and (b) U+U collisions at $\sqrt{s}$ = 200 GeV at midrapidity

Invariant transverse momentum spectra measured for $\phi$ mesons in (c) Cu+Au and (d) U+U collisions at $\sqrt{s}$ = 200 GeV at midrapidity. Data-to- Levy fit ratios.

The $\phi$-meson nuclear modification factors $R_{AB}$ measured as a function of $p_T$ in different centrality intervals of (a) to (d) Cu+Au collisions at $\sqrt{s}$ = 200 GeV and (e) to (h) U+U collisions at $\sqrt{s}$ = 193 GeV at midrapidity $|\eta|<0.35$. The normalization uncertainty from p+p of about $\sim9.7\%$ is not shown.

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Nonprompt direct-photon production in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Acharya, U.A. ; Adare, A. ; Aidala, C. ; et al.
336 authors from 71 institutions, 26 pages, 30 figures, 4 tabels, 2014 data. Physical Review C. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html, 2022.
Inspire Record 2061074 DOI 10.17182/hepdata.129292

The measurement of the direct-photon spectrum from Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV is presented by the PHENIX collaboration using the external-photon-conversion technique for 0%--93% central collisions in a transverse-momentum ($p_T$) range of 0.8--10 GeV/$c$. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for $p_T<6$ GeV/$c$. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as $N_{\rm coll}$-scaled direct photons from $p$ $+$ $p$ collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for $0.8<p_T<6.0$ GeV/$c$ and suggest that the spectrum has an increasing inverse slope from ${\approx}0.2$ to 0.4 GeV/$c$ with increasing $p_T$, which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the $p_T$-integrated nonprompt direct-photon yields also follow a power-law scaling behavior as a function of collision-system size. The exponent, $\alpha$, for the nonprompt component is found to be consistent with 1.1 with no apparent $p_T$ dependence.

9 data tables

Direct photon $R_{\gamma}$, every 20% centrality

Direct photon $R_{\gamma}$, every 10% centrality

Invariant yield of direct photons, every 10% centrality

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Low-$p_T$ direct-photon production in Au$+$Au collisions at $\sqrt{s_{_{NN}}}=39$ and 62.4 GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Adare, A. ; et al.
Phys.Rev.C 107 (2023) 024914, 2023.
Inspire Record 2057344 DOI 10.17182/hepdata.133218

The measurement of direct photons from Au$+$Au collisions at $\sqrt{s_{_{NN}}}=39$ and 62.4 GeV in the transverse-momentum range $0.4<p_T<3$ Gev/$c$ is presented by the PHENIX collaboration at the Relativistic Heavy Ion Collider. A significant direct-photon yield is observed in both collision systems. A universal scaling is observed when the direct-photon $p_T$ spectra for different center-of-mass energies and for different centrality selections at $\sqrt{s_{_{NN}}}=62.4$ GeV is scaled with $(dN_{\rm ch}/d\eta)^{\alpha}$ for $\alpha=1.21{\pm}0.04$. This scaling also holds true for direct-photon spectra from Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV measured earlier by PHENIX, as well as the spectra from Pb$+$Pb at $\sqrt{s_{_{NN}}}=2760$ GeV published by ALICE. The scaling power $\alpha$ seems to be independent of $p_T$, center of mass energy, and collision centrality. The spectra from different collision energies have a similar shape up to $p_T$ of 2 GeV/$c$. The spectra have a local inverse slope $T_{\rm eff}$ increasing with $p_T$ of $0.174\pm0.018$ GeV/$c$ in the range $0.4<p_T<1.3$ GeV/$c$ and increasing to $0.289\pm0.024$ GeV/$c$ for $0.9<p_T<2.1$ GeV/$c$. The observed similarity of low-$p_T$ direct-photon production from $\sqrt{s_{_{NN}}}= 39$ to 2760 GeV suggests a common source of direct photons for the different collision energies and event centrality selections, and suggests a comparable space-time evolution of direct-photon emission.

12 data tables

$R_{\gamma}$ for minimum bias (0-86%) Au+Au collision at $\sqrt{s_{NN}} = 62.4$ GeV (a) and $39$ GeV (b). For $62.4$ GeV also centrality bins of 0-20% (c) and 20-40% (d) are shown. Data points are shown with statistical (bar) and systematic uncertainties (box)

$R_{\gamma}$ for minimum bias (0-86%) Au+Au collision at $\sqrt{s_{NN}} = 62.4$ GeV (a) and $39$ GeV (b). For $62.4$ GeV also centrality bins of 0-20% (c) and 20-40% (d) are shown. Data points are shown with statistical (bar) and systematic uncertainties (box)

Direct photon spectra for minimum bias (0-86%) Au+Au collision at $\sqrt{s_{NN}} = 62.4$ GeV (a) and $39$ GeV (b). For $62.4$ GeV also centrality bins of 0-20% (c) and 20-40% (d) are shown. Data points are shown with statistical and systematic uncertainties, unless the central value is negative (arrows) or is consistent with zero within the statistical uncertainties (arrows with data point). In these cases upper limit with CL = 95$%$ are given.

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Measurements of second-harmonic Fourier coefficients from azimuthal anisotropies in $p+p, p$+Au $d$+Au, and $^3$He + Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Abdulameer, N.J. ; Acharya, U. ; Adare, A. ; et al.
Phys.Rev.C 107 (2023) 024907, 2023.
Inspire Record 2054927 DOI 10.17182/hepdata.136560

Recently, the PHENIX Collaboration has published second- and third-harmonic Fourier coefficients $v_2$ and $v_3$ for midrapidity ($|\eta|<0.35$) charged hadrons in 0%--5% central $p$$+$Au, $d$ $+$Au, and $^3$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV utilizing three sets of two-particle correlations for two detector combinations with different pseudorapidity acceptance [Phys. Rev. C {\bf 105}, 024901 (2022)]. This paper extends these measurements of $v_2$ to all centralities in $p$ $+$Au, $d$ $+$Au, and $^3$He$+$Au collisions, as well as $p$$+$$p$ collisions, as a function of transverse momentum ($p_T$) and event multiplicity. The kinematic dependence of $v_2$ is quantified as the ratio $R$ of $v_2$ between the two detector combinations as a function of event multiplicity for $0.5$ $<$ $p_T$ $<$ $1$ and $2$ $<$ $p_T$ $<$ $2.5$ GeV/$c$. A multiphase-transport (AMPT) model can reproduce the observed $v_2$ in most-central to midcentral $d$$+$Au and $^3$He$+$Au collisions. However, the AMPT model systematically overestimates the measurements in $p$ $+$ $p$, $p$ $+$Au, and peripheral $d$$+$Au and $^3$He$+$Au collisions, indicating a higher nonflow contribution in AMPT than in the experimental data. The AMPT model fails to describe the observed $R$ for $0.5$ $<$ $p_T$$<$ $1$ GeV/$c$, but there is qualitative agreement with the measurements for $2$ $<$ $p_T$ $<$ $2.5$ GeV/$c$.

18 data tables

Azimuthal anisotropy $v_2\{BB\}$ as a function of transverse momentum $p_T$ in $p$+Au collisions at $\sqrt{s_{NN}} =$ 200 GeV.

Azimuthal anisotropy $v_2\{BF\}$ as a function of transverse momentum $p_T$ in $p$+Au collisions at $\sqrt{s_{NN}} =$ 200 GeV.

Azimuthal anisotropy $v_2\{BB\}$ as a function of transverse momentum $p_T$ in $d$+Au collisions at $\sqrt{s_{NN}} =$ 200 GeV.

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Study of $\phi$-meson production in $p+$Al, $p+$Au, $d+$Au, and $^3$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Acharya, U. ; Adare, A. ; Aidala, C. ; et al.
Phys.Rev.C 106 (2022) 014908, 2022.
Inspire Record 2050486 DOI 10.17182/hepdata.130267

Small nuclear collisions are mainly sensitive to cold-nuclear-matter effects; however, the collective behavior observed in these collisions shows a hint of hot-nuclear-matter effects. The identified-particle spectra, especially the $\phi$ mesons which contain strange and antistrange quarks and have a relatively small hadronic-interaction cross section, are a good tool to study these effects. The PHENIX experiment has measured $\phi$ mesons in a specific set of small collision systems $p$$+$Al, $p$$+$Au, and $^3$He$+$Au, as well as $d$$+$Au [Phys. Rev. C {\bf 83}, 024909 (2011)], at $\sqrt{s_{_{NN}}}=200$ GeV. The transverse-momentum spectra and nuclear-modification factors are presented and compared to theoretical-model predictions. The comparisons with different calculations suggest that quark-gluon plasma may be formed in these small collision systems at $\sqrt{s_{_{NN}}}=200$ GeV. However, the volume and the lifetime of the produced medium may be insufficient for observing strangeness-enhancement and jet-quenching effects. Comparison with calculations suggests that the main production mechanisms of $\phi$ mesons at midrapidity may be different in $p$$+$Al versus $p/d/$$^3$He$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. While thermal quark recombination seems to dominate in $p/d/$$^3$He$+$Au collisions, fragmentation seems to be the main production mechanism in $p$$+$Al collisions.

2 data tables

Invariant transverse momentum spectra measured for $\phi$ mesons in (a) $p$+Al, (b) $p$+Au, and (c) $^{3}$He+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV at midrapidity.

Comparison of $\phi$-meson nuclear-modification factors in $p$+Al, $p$+Au, $d$+Au [2], and $^{3}$He+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV at midrapidity. The normalization uncertainty from $p$+$p$ of about $9.7 \%$ is not shown [28].


Measurement of Direct-Photon Cross Section and Double-Helicity Asymmetry at $\sqrt{s}=510$ GeV in $\vec{p}+\vec{p}$ Collisions

The PHENIX collaboration Acharya, U. ; Adare, A. ; Aidala, C. ; et al.
Phys.Rev.Lett. 130 (2023) 251901, 2023.
Inspire Record 2033856 DOI 10.17182/hepdata.129088

We present measurements of the cross section and double-helicity asymmetry $A_{LL}$ of direct-photon production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV. The measurements have been performed at midrapidity ($|\eta|<0.25$) with the PHENIX detector at the Relativistic Heavy Ion Collider. At relativistic energies, direct photons are dominantly produced from the initial quark-gluon hard scattering and do not interact via the strong force at leading order. Therefore, at $\sqrt{s}=510$ GeV, where leading-order-effects dominate, these measurements provide clean and direct access to the gluon helicity in the polarized proton in the gluon-momentum-fraction range $0.02<x<0.08$, with direct sensitivity to the sign of the gluon contribution.

2 data tables

Cross sections for inclusive and isolated direct photons as a function of $p_T$. Not shown are 10% absolute luminosity uncertainties.

Double helicity asymmetry $A_{LL}$ $vs$ $p_{T}$ for isolated direct-photon production in polarized $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=510$ GeV at midrapidity. Not shown are $3.9 \times 10^{-4}$ shift uncertainty from relative luminosity and 6.6% scale uncertainty from polarization.


Measurement of $\psi(2S)$ nuclear modification at backward and forward rapidity in $p$ $+$ $p$, $p$ $+$ Al, and $p$ $+$ Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

The PHENIX collaboration Acharya, U.A. ; Aidala, C. ; Akiba, Y. ; et al.
Phys.Rev.C 105 (2022) 064912, 2022.
Inspire Record 2029951 DOI 10.17182/hepdata.130200

Suppression of the $J/\psi$ nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the $\psi(2S)$ state in $p/d$ $+$ $A$ collisions suggested the presence of final-state effects. Results of $J/\psi$ and $\psi(2S)$ measurements in the dimuon decay channel are presented here for $p$ $+$ $p$, $p$ $+$Al, and $p$ $+$Au collision systems at $\sqrt{s_{_{NN}}}=200$ GeV. The results are predominantly shown in the form of the nuclear-modification factor, $R_{pA}$, the ratio of the $\psi(2S)$ invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in $p$ $+$ $p$ collisions. Measurements of the $J/\psi$ and $\psi(2S)$ nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large-Hadron-Collider energies.

12 data tables

PSI(2S)-->MU+MU- invariant yields in p+p, p+Al, and p+Au collisions as a function of 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(1S)-->MU+MU- invariant yields in p+p, p+Al, and p+Au collisions as a function of 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.

PSI(2S)-->MU+MU- nuclear modification in p+Al collisions as a function of 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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