-
A Adare,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
R Akimoto,
H Al-Ta'ani,
J Alexander,
K R Andrews,
A Angerami, [......],
J S Yoo,
Z You,
G R Young,
I Younus,
I E Yushmanov,
W A Zajc, A Zelenski,
S Zhou,
L Zolin,
PHENIX Collaboration
[show abstract]
[hide abstract]
ABSTRACT: We report on the first measurement of the double-spin asymmetry, A(LL), of electrons from the decays of hadrons containing heavy flavor in longitudinally polarized p + p collisions at root s = 200 GeV for p(T) = 0.5 to 3.0 GeV/c. The asymmetry was measured at midrapidity (vertical bar eta vertical bar < 0.35) with the PHENIX detector at the Relativistic Heavy Ion Collider. The measured asymmetries are consistent with zero within the statistical errors. We obtained a constraint for the polarized gluon distribution in the proton of vertical bar Delta g/g(log(10)(x) = -1.6(-0.4)(+0.5), mu = m(T)(c)vertical bar(2) < 0.030 (1 sigma) based on a leading-order perturbative quantum chromodynamics model, using the measured asymmetry. DOI: 10.1103/PhysRevD.87.012011
Physical Review D 01/2013; 87(1). · 4.56 Impact Factor
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Bataineh,
H. Al-Ta'ani,
J. Alexander,
A. Angerami, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke, A. Zelenski,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The jet fragmentation function is measured with direct photon-hadron
correlations in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The p_T of the
photon is an excellent approximation to the initial p_T of the jet and the
ratio z_T=p_T^h/p_T^\gamma is used as a proxy for the jet fragmentation
function. A statistical subtraction is used to extract the direct photon-hadron
yields in Au+Au collisions while a photon isolation cut is applied in p+p. I_
AA, the ratio of jet fragment yield in Au+Au to that in p+p, indicates
modification of the jet fragmentation function. Suppression, most likely due to
energy loss in the medium, is seen at high z_T. The fragment yield at low z_T
is enhanced at large angles. Such a trend is expected from redistribution of
the lost energy into increased production of low-momentum particles.
12/2012;
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Bataineh,
H. Al-Ta'ani,
J. Alexander,
K. R. Andrews, [......],
Z. You,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke, A. Zelenski,
C. Zhang,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: The three Upsilon states, Upsilon(1S+2S+3S), are measured in d+Au and p+p
collisions at sqrt(s_NN)=200 GeV and rapidities 1.2<|y|<2.2 by the PHENIX
experiment at the Relativistic Heavy-Ion Collider. Cross sections for the
inclusive Upsilon(1S+2S+3S) production are obtained. The inclusive yields per
binary collision for d+Au collisions relative to those in p+p collisions
(R_dAu) are found to be 0.62 +/- 0.26 (stat) +/- 0.13 (syst) in the gold-going
direction and 0.91 +/- 0.33 (stat) +/- 0.16 (syst) in the deuteron-going
direction. The measured results are compared to a nuclear-shadowing model,
EPS09 [JHEP 04, 065 (2009)], combined with a final-state breakup cross section,
sigma_br, and compared to lower energy p+A results. We also compare the results
to the PHENIX J/psi results [Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity
dependence of the observed Upsilon suppression is consistent with lower energy
p+A measurements.
11/2012;
-
A Adare,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
R Akimoto,
H Al-Ta'ani,
J Alexander,
A Angerami,
K Aoki, [......],
R Yang,
A Yanovich,
J Ying,
S Yokkaichi,
Z You,
I Younus,
I E Yushmanov,
W A Zajc, A Zelenski,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Neutral-pion π^{0} spectra were measured at midrapidity (|y|<0.35) in Au+Au collisions at sqrt[s_{NN}]=39 and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of 1<p_{T}<10 GeV/c. The high-p_{T} tail is well described by a power law in all cases, and the powers decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that observed in the corresponding spectra for p+p collisions. The nuclear modification factors (R_{AA}) show significant suppression, with a distinct energy, centrality, and p_{T} dependence. Above p_{T}=7 GeV/c, R_{AA} is similar for sqrt[s_{NN}]=62.4 and 200 GeV at all centralities. Perturbative-quantum-chromodynamics calculations that describe R_{AA} well at 200 GeV fail to describe the 39 GeV data, raising the possibility that, for the same p_{T} region, the relative importance of initial-state effects and soft processes increases at lower energies. The p_{T} range where π^{0} spectra in central Au+Au collisions have the same power as in p+p collisions is ≈5 and 7 GeV/c for sqrt[s_{NN}]=200 and 62.4 GeV, respectively. For the sqrt[s_{NN}]=39 GeV data, it is not clear whether such a region is reached, and the x_{T} dependence of the x_{T}-scaling power-law exponent is very different from that observed in the sqrt[s_{NN}]=62 and 200 GeV data, providing further evidence that initial-state effects and soft processes mask the in-medium suppression of hard-scattered partons to higher p_{T} as the collision energy decreases.
Physical Review Letters 10/2012; 109(15):152301. · 7.37 Impact Factor
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Taani,
J. Alexander,
A. Angerami,
K. Aoki, [......],
R. Yang,
A. Yanovich,
J. Ying,
S. Yokkaichi,
Z. You,
I. Younus,
I. E. Yushmanov,
W. A. Zajc, A. Zelenski,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: Neutral-pion �pi^0 spectra were measured at midrapidity (jyj < 0:35) in Au + Au collisions at sqrt(s_NN) = 39
and 62.4 GeV and compared with earlier measurements at 200 GeV in a transverse-momentum range of
1<pT < 10 GeV/c. The high - pT tail is well described by a power law in all cases, and the powers
decrease significantly with decreasing center-of-mass energy. The change of powers is very similar to that
observed in the corresponding spectra for p + p collisions. The nuclear modification factors (RAA) show
significant suppression, with a distinct energy, centrality, and pT dependence. Above pT =7 GeVc, RAA
is similar for sqrt(s_NN) = 62.4 and 200 GeV at all centralities. Perturbative-quantum-chromodynamics
calculations that describe RAA well at 200 GeV fail to describe the 39 GeV data, raising the possibility
that, for the same pT region, the relative importance of initial-state effects and soft processes increases at
lower energies. The pT range where pi^�0 spectra in central Au + Au collisions have the same power as in
p + p collisions is � 5 and 7 GeV/c for sqrt(s_NN) = 200 and 62.4 GeV, respectively. For the sqrt(s_NN) = 39 GeV data, it is not clear whether such a region is reached, and the xT dependence of the xT-scaling
power-law exponent is very different from that observed in the sqrt(s_NN) = 62 and 200 GeV data, providing
further evidence that initial-state effects and soft processes mask the in-medium suppression of hard scattered partons to higher pT as the collision energy decreases.
Physical Review Letters 10/2012; 109:152301. · 7.37 Impact Factor
-
A. Adare,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Ta'ani,
J. Alexander,
K. R. Andrews,
A. Angerami, [......],
S. Yokkaichi,
J. S. Yoo,
Z. You,
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc, A. Zelenski,
S. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: We report on the first measurement of double-spin asymmetry, A_LL, of
electrons from the decays of hadrons containing heavy flavor in longitudinally
polarized p+p collisions at sqrt(s)=200 GeV for p_T= 0.5 to 3.0 GeV/c. The
asymmetry was measured at mid-rapidity (|eta|<0.35) with the PHENIX detector at
the Relativistic Heavy Ion Collider. The measured asymmetries are consistent
with zero within the statistical errors. We obtained a constraint for the
polarized gluon distribution in the proton of |Delta g/g(log{_10}x=
-1.6^+0.5_-0.4, {mu}=m_T^c)|^2 < 0.033 (1 sigma), based on a leading-order
perturbative-quantum-chromodynamics model, using the measured asymmetry.
09/2012;
-
A. Adare,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
H. Al-Ta'ani,
J. Alexander,
A. Angerami,
K. Aoki,
N. Apadula, [......],
Y. L. Yamaguchi,
R. Yang,
A. Yanovich,
J. Ying,
S. Yokkaichi,
Z. You,
I. Younus,
I. E. Yushmanov,
W. A. Zajc, A. Zelenski
[show abstract]
[hide abstract]
ABSTRACT: We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and
62.4 GeV Au+Au collisions at forward rapidity (1.2<|y|<2.2). Invariant yields
are presented as a function of both collision centrality and transverse
momentum. Nuclear modifications are obtained for central relative to peripheral
Au+Au collisions (R_CP) and for various centrality selections in Au+Au relative
to scaled p+p cross sections obtained from other measurements (R_AA). The
observed suppression patterns at 39 and 62.4 GeV are quite similar to those
previously measured at 200 GeV. This similar suppression presents a challenge
to theoretical models that contain various competing mechanisms with different
energy dependencies, some of which cause suppression and others enhancement.
08/2012;
-
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
R. Akimoto,
J. Alexander,
K. Aoki,
N. Apadula,
H. Asano,
E. T. Atomssa,
T. C. Awes, [......],
I. Yoon,
M. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
E. Zarndt, A. Zelenski,
L. Zhang,
S. Zhou,
C. Zumberge
[show abstract]
[hide abstract]
ABSTRACT: The PHENIX collaboration presents a concept for a major upgrade to the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). This upgrade, referred to as sPHENIX, brings exciting new capability to the RHIC program by opening new and important channels for experimental investigation and utilizing fully the luminosity of the recently upgraded RHIC facility. sPHENIX enables a compelling jet physics program that will address fundamental questions about the nature of the strongly coupled quark-gluon plasma discovered experimentally at RHIC to be a perfect fluid. The upgrade concept addresses specific questions whose answers are necessary to advance our understanding of the quark-gluon plasma: (1) How to reconcile the observed strongly coupled quark-gluon plasma with the asymptotically free theory of quarks and gluons? (2) What are the dynamical changes to the quark-gluon plasma in terms of quasiparticles and excitations as a function of temperature? (3) How sharp is the transition of the quark-gluon plasma from the most strongly coupled regime near Tc to a weakly coupled system of partons known to emerge at asymptotically high temperatures? In three Appendices, we detail the additional physics capabilities gained through further upgrades: (A) two midrapidity detector additions, (B) a forward rapidity upgrade, and (C) an evolution to an ePHENIX detector suitable for a future Electron Ion Collider at RHIC.
Nuclear Physics A 08/2012; · 1.54 Impact Factor
-
D. Boer,
M. Diehl,
R. Milner,
R. Venugopalan,
W. Vogelsang,
A. Accardi,
E. Aschenauer,
M. Burkardt,
R. Ent,
V. Guzey, [......],
S. Webb,
C Weiss,
Q Wu,
B. -W. Xiao,
W Xu,
B. Yunn, A. Zelenski,
Y Zhang,
J Zhou,
P. Zurita
[show abstract]
[hide abstract]
ABSTRACT: This report is based on a ten-week program on "Gluons and the quark sea at
high-energies", which took place at the Institute for Nuclear Theory in Seattle
in Fall 2010. The principal aim of the program was to develop and sharpen the
science case for an Electron-Ion Collider (EIC), a facility that will be able
to collide electrons and positrons with polarized protons and with light to
heavy nuclei at high energies, offering unprecedented possibilities for
in-depth studies of quantum chromodynamics. This report is organized around
four major themes: i) the spin and flavor structure of the proton, ii)
three-dimensional structure of nucleons and nuclei in momentum and
configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and
the search for physics beyond the Standard Model. Beginning with an executive
summary, the report contains tables of key measurements, chapter overviews for
each of the major scientific themes, and detailed individual contributions on
various aspects of the scientific opportunities presented by an EIC.
08/2011;
-
D. Boer,
M. Diehl,
R. Milner,
R. Venugopalan,
W. Vogelsang,
A. Accardi,
E. Aschenauer,
M. Burkardt,
R. Ent,
V. Guzey, [......],
S. Webb,
C. Weiss,
Q. Wu,
B.-W. Xiao,
W. Xu,
B. Yunn, A. Zelenski,
Y. Zhang,
J. Zhou,
P. Zurita
[show abstract]
[hide abstract]
ABSTRACT: This report is based on a ten-week program on "Gluons and the quark sea
at high-energies", which took place at the Institute for Nuclear Theory
in Seattle in Fall 2010. The principal aim of the program was to develop
and sharpen the science case for an Electron-Ion Collider (EIC), a
facility that will be able to collide electrons and positrons with
polarized protons and with light to heavy nuclei at high energies,
offering unprecedented possibilities for in-depth studies of quantum
chromodynamics. This report is organized around four major themes: i)
the spin and flavor structure of the proton, ii) three-dimensional
structure of nucleons and nuclei in momentum and configuration space,
iii) QCD matter in nuclei, and iv) Electroweak physics and the search
for physics beyond the Standard Model. Beginning with an executive
summary, the report contains tables of key measurements, chapter
overviews for each of the major scientific themes, and detailed
individual contributions on various aspects of the scientific
opportunities presented by an EIC.
07/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: The RHIC polarized H− ion source is being upgraded to higher intensity (5-10 mA) and polarization for use in the RHIC polarization physics program at enhanced luminosity RHIC operation. The higher beam peak intensity will allow reduction of the transverse beam emittance at injection to AGS to reduce polarization losses in AGS. There is also a planned RHIC luminosity upgrade by using the electron beam lens to compensate the beam-beam interaction at collision points. This upgrade is also essential for future BNL plans for a high-luminosity electron – proton (ion) Collider eRHIC.
Journal of Physics Conference Series 05/2011; 295(1):012147.
-
Y Makdisi,
I Alekseev,
E Aschenauer,
G Atoian,
A Bazilevsky,
R Gill,
H Huang,
B Morozov,
D Svirida,
K Yip, A Zelenski
[show abstract]
[hide abstract]
ABSTRACT: The RHIC polarized proton complex utilizes polarimeters in each of the Blue and Yellow beams that measure the beam polarization through the p-Carbon elastic scattering process in the Coulomb Nuclear Interference kinematic region. This along with a Polarized Hydrogen Jet Target that utilizes the proton-proton elastic scattering process to first measure the analyzing power of the reaction and using the reverse process to measure the beam polarization. The latter is used to calibrate the p-Carbon polarimeters at the desired beam energy. In Run 9 RHIC ran with beams at center-of-mass energies of 200 and 500 GeV respectively. The higher beam intensities as well as the fact that the 250 GeV beam size is much smaller than that at 100 GeV resulted in significantly higher rates seen by the polarimeters and led to observed instability. In this paper, we will discuss the problems encountered and the tests that were carried out using the AGS as a proxy in an attempt to solve the problems and the path forward we took towards the upcoming polarized proton Run11.
Journal of Physics Conference Series 05/2011; 295(1):012130.
-
A Bazilevsky,
I Alekseev,
E Aschenauer,
G Atoyan,
A Bravar,
G Bunce,
K Boyle,
R Gill,
H Huang,
S Lee,
Y Makdisi,
B Morozov,
I Nakagawa,
H Okada,
D Svirida, A Zelenski
[show abstract]
[hide abstract]
ABSTRACT: We present new measurements of the analyzing power AN in proton-proton elastic scattering in the Coulomb-Nuclear Interference region at √s = 7.7 and 21.7 GeV obtained with the polarized atomic hydrogen jet target at RHIC. These measurements complement our earlier results at √s = 6.8 and 13.7 GeV confirming the presence of a hadronic helicity flip amplitude contribution in proton-proton elastic scattering at lower energies (√s <8 GeV) while higher energy data (√s >13 GeV) are consistent with no hadronic helicity flip contribution.
Journal of Physics Conference Series 05/2011; 295(1):012096.
-
[show abstract]
[hide abstract]
ABSTRACT: A new polarimeter for absolute proton beam polarization measurements at 200 MeV to accuracy better than ±0.5% has been developed as a part of the RHIC polarized source upgrade. The polarimeter is based on the elastic proton-carbon scattering at 16.2° angle, where the analyzing power is close to 100% and was measured with high accuracy. The elastically and in-elastically scattered protons are clearly identified by the difference in the propagation through variable copper absorber and energy deposition of the protons in the detectors. The elastic scattering polarimeter was used for calibration of a high rate inclusive 12° polarimer for the on-line polarization tuning and monitoring. This technique can be used for accurate polarization measurements in energy range of at least 160–250 MeV.
Journal of Physics Conference Series 05/2011; 295(1):012132.
-
M Bai,
L Ahrens,
I G Alekseev,
J Alessi,
E Courant,
A Drees,
W Fischer,
C Gardner,
R Gill,
J Glenn, [......],
V Ptitsyn,
T Roser,
D Svirida,
T Satogata,
S Tepikian,
D Trbojevic,
N Tsoupas, A Zelenski,
K Zeno,
S Y Zhang
[show abstract]
[hide abstract]
ABSTRACT: The Siberian snakes are powerful tools in preserving polarization in high energy accelerators has been demonstrated at the Brookhaven Relativistic Heavy Ion Collider (RHIC). Equipped with two full Siberian snakes in each ring, polarization is preserved during acceleration from injection to 100 GeV. However, the Siberian snakes also introduce a new set of depolarization resonances, i.e. snake resonances as first discoverd by Lee and Tepikian [1]. The intrinsic spin resonances above 100 GeV are about a factor of two stronger than those below 100 GeV which raises the challenge to preserve the polarization up to 250 GeV. In 2009, polarized protons collided for the first time at the RHIC design store energy of 250 GeV. This paper presents the experimental measurements of snake resonances at RHIC. The plan for avoiding these resonanances is also presented.
Journal of Physics Conference Series 05/2011; 295(1):012142.
-
A Adare,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
R Akimoto,
J Alexander,
H Al-Ta'ani,
K R Andrews,
A Angerami, [......],
S Yokkaichi,
J S Yoo,
G R Young,
I Younus,
Z You,
I E Yushmanov,
W A Zajc, A Zelenski,
S Zhou,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ¯](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb.
Physical Review Letters 02/2011; 106(6):062001. · 7.37 Impact Factor
-
A. Adare,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
R Akimoto,
J Alexander,
H. Al-Taani,
K. R. Andrews,
A. Angerami, [......],
S Yokkaichi,
J S Yoo,
G R Young,
I. Younus,
Z You,
I E Yushmanov,
W A Zajc, A. Zelenski,
S Zhou,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Large parity violating longitudinal single spin asymmetries A^{e^-}_L=
-0.86^{+0.14}_{-0.30} and A^{e^+}_L= 0.88^{+0.12}_{-0.71} are observed for
inclusive high transverse momentum electrons and positrons in polarized pp
collisions at a center of mass energy of \sqrt{s}=500\ GeV with the PHENIX
detector at RHIC. These e^{+/-} come mainly from the decay of W^{+/-} and Z^0
bosons, and the asymmetries directly demonstrate parity violation in the
couplings of the W^{\pm} to the light quarks. The observed electron and
positron yields were used to estimate W^\pm boson production cross sections
equal to \sigma(pp \to W^+ X) \times BR(W^ \to \nu_e)=
144.1+/-21.2(stat)^{+3.4}_{-10.3}(syst) +/- 15%(norm) pb, and \sigma(pp \to
W^{-}X) \times BR(W^\to e^-\bar{\nu_e}) =
31.7+/-12.1(stat)^{+10.1}_{-8.2}(syst)+/-15%(norm) pb.
09/2010;
-
A Zelenski
[show abstract]
[hide abstract]
ABSTRACT: Recent progress in polarized ion sources development is reviewed. New techniques for production of polarized H(-) ion (proton), D(-) (D(+)), and (3)He(++) ion beams are discussed. Feasibility studies of these techniques are in progress at BNL and other laboratories. Polarized deuteron beams will be required for the polarization program at the Dubna Nuclotron and at the deuteron electric dipole moment experiment at BNL. Experiments with polarized (3)He(++) ion beams are a part of the experimental program at the future electron ion collider.
The Review of scientific instruments 02/2010; 81(2):02B308. · 1.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The depolarization factors in the multi‐step spin‐transfer polarization technique and basic limitations on maximum polarization in the Optically‐Pumped Polarized H‐ Ion Source (OPPIS) are discussed. Results of simulations and experimental studies of the Sona‐transition polarization transfer process are presented. The experimentally observed polarization oscillations and polarization maximum peak were reproduced in simulations. Detailed studies of polarization losses in the RHIC OPPIS and the source parameters optimization resulted in the OPPIS polarization increase to 86–90%. This contributed to increasing polarization in the AGS and RHIC to 65∼70%.
AIP Conference Proceedings. 08/2009; 1149(1):847-852.
-
[show abstract]
[hide abstract]
ABSTRACT: The RHIC polarized proton collider polarimeters employ the analyzing power in p‐Carbon elastic scattering in the Coulomb Nuclear Interference region to measure the proton beam polarization. These are calibrated by the polarized hydrogen jet target that measures the absolute beam polarization utilizing the pp elastic scattering process in the CNI region. This paper describes the status of these polarimeters and the efforts employed to improve the performance in terms of better resolution, rate handling capability, and reduced systematic uncertainties.
AIP Conference Proceedings. 08/2009; 1149(1):727-730.
