Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userAbsolute polarimetry at RHIC
225
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy of $Delta P_{beam}/P_{beam} < 5%$. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features textit{proton-proton} elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power $A_N$ of this process has allowed us to achieve $Delta P_{beam}/P_{beam} =4.2%$ in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of $A_N$ in the CNI region (four-momentum transfer squared $0.001 < -t < 0.032 ~ ({rm GeV}/c)^2$) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.
rate research
Read More
Recent soft physics results from collisions of ultra-relativistic nuclei at Relativistic Heavy Ion Collider (RHIC) operating at Brookhaven National Laboratory (BNL) are reviewed. Topics discussed cover the Beam Energy Scan program with some emphasis on anisotropic particle flow.
We present the recent results of strangeness production at the mid-rapidity in Au + Au collisions at RHIC, from $sqrt{s_{rm NN}}$ = 7.7 to 200 GeV. The $v_2$ of multi-strange baryon $Omega$ and $phi$ mesons are similar to that of pions and protons in the intermediate $p_T$ range (2 - 5 GeV/$c$) in $sqrt{s_{rm NN}}$ = 200 GeV Au + Au collisions, indicating that the major part of collective flow has been built up at partonic stage. The breaking of mass ordering between $phi$ mesons and protons in the low $p_T$ range ($<$ 1 GeV/$c$) is consistent with a picture that $phi$ mesons are less sensitive to later hadronic interaction. The nuclear modification factor $R_{rm CP}$ and baryon to meson ratio change dramatically when the collision energy is lower than 19.6 GeV. It suggests a possible change of medium property of the system compared to those from high energies.
In this report, we present the measurements of open charm production at mid-rapidity in p+p, d+Au, and Au+Au collisions at RHIC energies. The techniques of direct reconstruction of open charm via its hadronic decay and indirect measurements through its semileptonic decay are discussed. The beam energy dependence of total charm cross section, electron pt spectra, and their comparisons to theoretical calculations, including NLO pQCD, are presented. The electron spectra in p+p, d+Au, and Au+Au collisions at srt=200 GeV show significant variation. The open charm absolute cross section at midrapidity and its centrality dependence are compared to those of inclusive hadrons integrated over $p_{T}>1.5$ GeV/c.
Large proton and antiproton enhancement with respect to pions has been observed at intermediate transverse momentum $p_T approx$ 2-5 GeV/$c$ in Au+Au collisions at RHIC. To investigate the possible source of this anomaly, the production of $phi$ mesons and two particle angular correlations triggered by mid-$p_T$ baryons or mesons are studied. We also present the first measurement of proton and antiproton production at $sqrt{s_{NN}} = 62.4$ GeV in Au+Au collisions, which aims to study the energy dependence of the observed baryon enhancement.
The J/psi is considered to be among the most important probes for the deconfined quark gluon plasma (QGP) created by relativistic heavy ion collisions. While the J/psi is thought to dissociate in the QGP by Debye color screening, there are competing effects from cold nuclear matter (CNM), feed-downs from excited charmonia (chi_c and psi) and bottom quarks, and regeneration from uncorrelated charm quarks. Measurements that can provide information to disentangle these effects are presented in this paper.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
