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Register a new userComparative study of the inclusive asymmetries induced by polarized protons and antiprotons at 16 GeV/$c$ at the U-70 accelerator
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The only comparative study of the inclusive pion single-spin asymmetries produced in the interactions of the polarized protons and antiprotons in collisions with unpolarized proton was carried out at E-704 experiment. Significant asymmetries were found at large $x_{F}$ and middle $p_{T}$, $pi^{+}$ and $pi^{0}$ asymmetries have positive signs while $pi^{-}$ has negative one in the $p^{uparrow}+p$ collisions, while in the $bar{p}^{uparrow}+p$ interactions the $pi^{-}$ and $pi^{0}$ asymmetries have positive signs while $pi^{+}$ has negative sign. Similar experimental study can be done in the SPASCHARM experiment at U-70 accelerator at IHEP for various secondary particles with the use of 16 GeV polarized proton and antiproton beams.
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The production of protons, anti-protons, neutrons, deuterons and tritons in minimum bias p+C interactions is studied using a sample of 385 734 inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The data cover a phase space area ranging from 0 to 1.9 GeV/c in transverse momentum and in Feynman x from -0.80 to 0.95 for protons, from -0.2 to 0.4 for anti-protons and from 0.2 to 0.95 for neutrons. Existing data in the far backward hemisphere are used to extend the coverage for protons and light nuclear fragments into the region of intranuclear cascading. The use of corresponding data sets obtained in hadron-proton collisions with the same detector allows for the detailed analysis and model-independent separation of the three principle components of hadronization in p+C interactions, namely projectile fragmentation, target fragmentation of participant nucleons and intranuclear cascading.
Single Spin Asymmetries (SSA) $A_N$ measured in the two reactions at the Protvino 70 GeV accelerator are presented. $A_N$ in the reaction $p+p(pol)->pi^0+X$ in the central region is close to zero within the error bars. SSA in the reaction $pi^- +p(pol)->pi^0+X$ in the polarized target fragmentation region is equal to $(-15 pm 4)%$ at $|x_F|>0.4$. There is an indication that the asymmetry arises at the same pion energy in the center of mass system.
The design and parameters of the polarized-beam facility at U-70 proton synchrotron of NRC Kurchatov Institute - IHEP are presented. The new beamline 24A will provide the polarized proton and antiproton beams for carrying out the rich physics program of the SPASCHARM experiment for comprehensive studies of spin phenomena in a wide spectrum of hadronic reactions in the energy range of 10-45 GeV.
We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet + $pi^{pm}$ production at midrapidity from transversely polarized proton-proton collisions at $sqrt{s} = 500$ GeV. The data were collected in 2011 with the STAR detector sampled from 23 pb$^{-1}$ integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta $6 < p_{T, jet} < 55$ GeV/c and pseudorapidity $|eta| < 1$. Presented are measurements of the inclusive-jet azimuthal transverse single-spin asymmetry, sensitive to twist-3 initial-state quark-gluon correlators; the Collins asymmetry, sensitive to quark transversity coupled to the polarized Collins fragmentation function; and the first measurement of the Collins-like asymmetry, sensitive to linearly polarized gluons. Within the present statistical precision, inclusive-jet and Collins-like asymmetries are small, with the latter allowing the first experimental constraints on gluon linear polarization in a polarized proton. At higher values of jet transverse momenta, we observe the first non-zero Collins asymmetries in polarized-proton collisions, with a statistical significance of greater than $5sigma$. The results span a range of x similar to results from SIDIS but at much higher $Q^{2}$. The Collins results enable tests of universality and factorization-breaking in the transverse momentum-dependent formulation of perturbative quantum chromodynamics.
We report the double helicity asymmetry, $A_{LL}^{J/psi}$, in inclusive $J/psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $sqrt{s}=510$ GeV longitudinally polarized $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision energy, $J/psi$ particles are predominantly produced through gluon-gluon scatterings, thus $A_{LL}^{J/psi}$ is sensitive to the gluon polarization inside the proton. We measured $A_{LL}^{J/psi}$ by detecting the decay daughter muon pairs $mu^+ mu^-$ within the PHENIX muon spectrometers in the rapidity range $1.2<|y|<2.2$. In this kinematic range, we measured the $A_{LL}^{J/psi}$ to be $0.012 pm 0.010$~(stat)~$pm$~$0.003$(syst). The $A_{LL}^{J/psi}$ can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken $x$: one at moderate range $x approx 0.05$ where recent RHIC data of jet and $pi^0$ double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-$x$ region $x approx 2times 10^{-3}$. Thus our new results could be used to further constrain the gluon polarization for $x< 0.05$.
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