Inclusive cross sections, charge ratio and double-helicity asymmetries for $\pi^+$ and $\pi^-$ production in $p$$+$$p$ collisions at $\sqrt{s}$=200 GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.D 91 (2015) 032001, 2015.
Inspire Record 1315330 DOI 10.17182/hepdata.71403

We present the midrapidity charged pion invariant cross sections and the ratio of $\pi^-$-to-$\pi^+$ production ($5<p_T<13$ GeV/$c$), together with the double-helicity asymmetries ($5<p_T<12$ GeV/$c$) in polarized $p$$+$$p$ collisions at $\sqrt{s} = 200$ GeV. The cross section measurements are consistent with perturbative calculations in quantum chromodynamics within large uncertainties in the calculation due to the choice of factorization, renormalization, and fragmentation scales. However, the theoretical calculation of the ratio of $\pi^-$-to-$\pi^+$ production when considering these scale uncertainties overestimates the measured value, suggesting further investigation of the uncertainties on the charge-separated pion fragmentation functions is needed. Due to cancellations of uncertainties in the charge ratio, direct inclusion of these ratio data in future parameterizations should improve constraints on the flavor dependence of quark fragmentation functions to pions. By measuring charge-separated pion asymmetries, one can gain sensitivity to the sign of $\Delta G$ through the opposite sign of the up and down quark helicity distributions in conjunction with preferential fragmentation of positive pions from up quarks and negative pions from down quarks. The double-helicity asymmetries presented are sensitive to the gluon helicity distribution over an $x$ range of $\sim$0.03--0.16.

3 data tables

Invariant cross section for $\pi^+$ and $\pi^-$ hadrons, as well as the statistical and systematic uncertainties. In addition, there is an absolute scale uncertainty of 9.6$\%$.

Double-helicity asymmetries and statistical uncertainties for $\pi^+$ and $\pi^-$ hadrons. The primary systematic uncertainties, which are fully correlated between points, are $1.4\times10^{-3}$ from relative luminosity and a $^{+7.0\%}_{-7.7\%}$ scaling uncertainty from beam polarization.

Ratio of charged pion cross section, as shown in Fig.6.


Cross Section and Transverse Single-Spin Asymmetry of $\eta$ Mesons in $p^{\uparrow}+p$ Collisions at $\sqrt{s}=200$ GeV at Forward Rapidity

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.D 90 (2014) 072008, 2014.
Inspire Record 1300542 DOI 10.17182/hepdata.64267

We present a measurement of the cross section and transverse single-spin asymmetry ($A_N$) for $\eta$ mesons at large pseudorapidity from $\sqrt{s}=200$~GeV $p^{\uparrow}+p$ collisions. The measured cross section for $0.5<p_T<5.0$~GeV/$c$ and $3.0<|\eta|<3.8$ is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries $A_N$ have been measured as a function of Feynman-$x$ ($x_F$) from $0.2<|x_{F}|<0.7$, as well as transverse momentum ($p_T$) from $1.0<p_T<4.5$~GeV/$c$. The asymmetry averaged over positive $x_F$ is $\langle{A_{N}}\rangle=0.061{\pm}0.014$. The results are consistent with prior transverse single-spin measurements of forward $\eta$ and $\pi^{0}$ mesons at various energies in overlapping $x_F$ ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in $p^{\uparrow}+p$ collisions.

4 data tables

The measured ETA meson cross section, E*D3(SIG)/DP**3, versus PT at forward rapidity. The statistical and systematic uncertainties are type-A and type-B uncertainties respectively.

ASYM(PEAK) and ASYM(BG) for ETA mesons measured as a function of XF in the range 0.3 < ABS(XF) < 0.7 from the 4X4B triggered dataset. The values represented are the weighted mean of the South and North MPC (Muon Piston Calorimeter). The uncertainties listed are statistical only.

ASYM for ETA mesons measured as a function of XF in the range 0.2 < ABS(XF) < 0.7. Uncertainties listed are those due to the statistics, the XF uncorrelated uncertainties due to extracting the yields, and the correlated relative luminosity uncertainty.

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Low-mass vector-meson production at forward rapidity in $p+p$ collisions at $\sqrt{s}=200$ GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.D 90 (2014) 052002, 2014.
Inspire Record 1296835 DOI 10.17182/hepdata.64159

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low mass vector meson, $\omega$, $\rho$, and $\phi$, production through the dimuon decay channel at forward rapidity ($1.2<|y|<2.2$) in $p$$+$$p$ collisions at $\sqrt{s}=200$ GeV. The differential cross sections for these mesons are measured as a function of both $p_T$ and rapidity. We also report the integrated differential cross sections over $1<p_T<7$ GeV/$c$ and $1.2<|y|<2.2$: $d\sigma/dy(\omega+\rho\rightarrow\mu\mu) = 80 \pm 6 \mbox{(stat)} \pm 12 \mbox{(syst)}$ nb and $d\sigma/dy(\phi\rightarrow\mu\mu) = 27 \pm 3 \mbox{(stat)} \pm 4 \mbox{(syst)}$ nb. These results are compared with midrapidity measurements and calculations.

3 data tables

Differential cross sections of (OMEGA + RHO) and PHI as functions of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.

Differential cross sections of (OMEGA + RHO) and PHI as functions of rapidity. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.

N(PHI) / ( N(OMEGA) + N(RHO) ) as a function of PT. The statistical uncertainty includes the type-A systematic uncertainty. The systematic uncertainty is the type-B systematic uncertainty.


Inclusive double-helicity asymmetries in neutral pion and eta meson production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200$ GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.D 90 (2014) 012007, 2014.
Inspire Record 1282448 DOI 10.17182/hepdata.64716

Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $\pi^0$ and $\eta$ production in $\sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisions. Comparison of the $\pi^0$ results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, $\Delta G$, in the proton in the probed Bjorken $x$ range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}} = 0.06^{+0.11}_{-0.15}$ in the range $0.05<x<0.2$, with the uncertainty at $\Delta \chi^2 = 9$ when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of $\Delta G^{[0.05,0.2]}_{\mbox{DSSV}}$ between $0.02$ and $0.12$, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.

9 data tables

PI0 ASYM(LL) measurements from 2005.

PI0 ASYM(LL) measurements from 2006.

PI0 ASYM(LL) measurements from 2009.

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Quadrupole anisotropy in dihadron azimuthal correlations in central d+Au collisions at sqrt(s_NN)=200 GeV

The PHENIX collaboration Adare, A. ; Aidala, C. ; Ajitanand, N.N. ; et al.
Phys.Rev.Lett. 111 (2013) 212301, 2013.
Inspire Record 1222874 DOI 10.17182/hepdata.62722

The PHENIX collaboration at the Relativistic Heavy Ion Collider (RHIC) reports measurements of azimuthal dihadron correlations near midrapidity in $d$$+$Au collisions at $\sqrt{s_{_{NN}}}$=200 GeV. These measurements complement recent analyses by experiments at the Large Hadron Collider (LHC) involving central $p$$+$Pb collisions at $\sqrt{s_{_{NN}}}$=5.02 TeV, which have indicated strong anisotropic long-range correlations in angular distributions of hadron pairs. The origin of these anisotropies is currently unknown. Various competing explanations include parton saturation and hydrodynamic flow. We observe qualitatively similar, but larger, anisotropies in $d$$+$Au collisions compared to those seen in $p$$+$Pb collisions at the LHC. The larger extracted $v_2$ values in $d$$+$Au collisions at RHIC are consistent with expectations from hydrodynamic calculations owing to the larger expected initial-state eccentricity compared with that from $p$$+$Pb collisions. When both are divided by an estimate of the initial-state eccentricity the scaled anisotropies follow a common trend with multiplicity that may extend to heavy ion data at RHIC and the LHC, where the anisotropies are widely thought to arise from hydrodynamic flow.

5 data tables

The second-order pair anisotropy, c2, of the central collision excess as a function of associated particle pT.

The third-order pair anisotropy, c3, of the central collision excess as a function of associated particle pT.

Charged hadron second-order anisotropy, v2, as a function of pT.

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Measurement of the $x$- and $Q^2$-Dependence of the Asymmetry $A_1$ on the Nucleon

The CLAS collaboration Dharmawardane, K.V. ; Kuhn, S.E. ; Bosted, Peter E. ; et al.
Phys.Lett.B 641 (2006) 11-17, 2006.
Inspire Record 717523 DOI 10.17182/hepdata.6726

We report results for the virtual photon asymmetry $A_1$ on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton ($^{15}$NH$_3$) and deuteron ($^{15}$ND$_3$) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present paper, we concentrate on our results for $A_1(x,Q^2)$ and the related ratio $g_1/F_1(x,Q^2)$ in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer $Q^2$ from 0.05 to 5.0 GeV$^2$ and in final-state invariant mass $W$ up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong $Q^2$--dependence of $A_1(x,Q^2)$ for $W$ below 2 GeV. At higher $W$, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but $A_1(x,Q^2)$ is not strictly $Q^2$--independent. We add significantly to the world data set at high $x$, up to $x = 0.6$. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative $d$-quark polarization up to our highest $x$. This data setshould improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.

306 data tables

A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1300 GeV.

A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1500 GeV.

A1 and g1/F1 for the P target at incident energy 1.6000 GeV and W = 1.1700 GeV.

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Measurement of the deuteron structure function F2 in the resonance region and evaluation of its moments.

The CLAS collaboration Osipenko, M. ; Ricco, G. ; Simula, S. ; et al.
Phys.Rev.C 73 (2006) 045205, 2006.
Inspire Record 684005 DOI 10.17182/hepdata.12254

Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasi-elastic peak up to the invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous measurements of the proton structure function F2 and cover a similar two-dimensional region of Q2 and Bjorken variable x. Determination of the deuteron F2 over a large x interval including the quasi-elastic peak as a function of Q2, together with the other world data, permit a direct evaluation of the structure function moments for the first time. By fitting the Q2 evolution of these moments with an OPE-based twist expansion we have obtained a separation of the leading twist and higher twist terms. The observed Q2 behaviour of the higher twist contribution suggests a partial cancellation of different higher twists entering into the expansion with opposite signs. This cancellation, found also in the proton moments, is a manifestation of the duality phenomenon in the F2 structure function.

113 data tables

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Measurement of the proton spin structure function g1(x,Q**2) for Q**2 from 0.15-GeV**2 to 1.6-GeV**2 with CLAS.

The CLAS collaboration Fatemi, R. ; Skabelin, A.V. ; Burkert, V.D. ; et al.
Phys.Rev.Lett. 91 (2003) 222002, 2003.
Inspire Record 621221 DOI 10.17182/hepdata.41917

Double-polarization asymmetries for inclusive $ep$ scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH$_3$ target in the CLAS detector. The polarized structure function $g_1(x,Q^2)$ was extracted throughout the nucleon resonance region and into the deep inelastic regime, for $Q^2 = 0.15 -1.64 $GeV$^2$. The contributions to the first moment $\Gamma_1(Q^2) = \int g_1(x,Q^2)dx$ were determined up to $Q^2=1.2$ GeV$^2$. Using a parametrization for $g_1$ in the unmeasured low $x$ regions, the complete first moment was estimated over this $Q^2$ region. A rapid change in $\Gamma_1$ is observed for $Q^2 < 1 $GeV$^2$, with a sign change near $Q^2 = 0.3 $GeV$^2$, indicating dominant contributions from the resonance region. At $Q^2=1.2$ GeV$^2$ our data are below the pQCD evolved scaling value.

8 data tables

The measured photon asymmetry (A1+ETA*A2) for the Q**2 region 0.15 to 0.22 GeV**2 obtained with a beam energy of 2.6 GeV.

The measured photon asymmetry (A1+ETA*A2) for the Q**2 region 0.6 to 1.10 GeV**2 obtained with a beam energy of 4.3 GeV.

The polarized structure function G1 as a function of Bjorken X for the Q**2range 0.15 to 0.27 GeV.

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A kinematically complete measurement of the proton structure function F2 in the resonance region and evaluation of its moments.

The CLAS collaboration Osipenko, M. ; Ricco, G. ; Taiuti, M. ; et al.
Phys.Rev.D 67 (2003) 092001, 2003.
Inspire Record 612145 DOI 10.17182/hepdata.12253

We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.

46 data tables

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Measurement of inclusive spin structure functions of the deuteron with CLAS.

The CLAS collaboration Yun, J. ; Kuhn, S.E. ; Dodge, G.E. ; et al.
Phys.Rev.C 67 (2003) 055204, 2003.
Inspire Record 604799 DOI 10.17182/hepdata.41972

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer ($Q^2$ = 0.27 -- 1.3 (GeV/c)$^2$) and final hadronic state mass in the nucleon resonance region ($W$ = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ($^{15}$ND$_3$) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d$. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ($Q^2 \to 0$). We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and 0.8 (GeV/c)$^2$, indicating the importance of the $\Delta$ resonance at these momentum transfers.

7 data tables

The measured virtual photon asymmetry (A1D+ETA*A2D) for the Q** region 0.27to 0.39 GeV**2.

The measured virtual photon asymmetry (A1D+ETA*A2D) for the Q** region 0.39to 0.65 GeV**2.

The measured virtual photon asymmetry (A1D+ETA*A2D) for the Q** region 0.65to 1.3 GeV**2.

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