-
A. Adare,
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
A. Al-Jamel,
J. Alexander,
A. Angerami, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: Direct photons have been measured in sqrt(s_NN)=200 GeV d+Au collisions at
midrapidity. A wide p_T range is covered by measurements of nearly-real virtual
photons (1<p_T<6 GeV/c) and real photons (5<p_T<16 GeV/c). The invariant yield
of the direct photons in d+Au collisions over the scaled p+p cross section is
consistent with unity. Theoretical calculations assuming standard cold nuclear
matter effects describe the data well for the entire p_T range. This indicates
that the large enhancement of direct photons observed in Au+Au collisions for
1.0<p_T<2.5 GeV/c is due to a source other than the initial-state nuclear
effects.
08/2012;
-
The CALICE collaboration,
C Adloff,
Y Karyotakis,
J Repond,
A Brandt,
H Brown,
K De,
C Medina,
J Smith,
J Li, [......],
I Kim,
T Lee,
J Park,
J Sung,
S Itoh,
K Kotera,
M Nishiyama,
T Takeshita,
S Weber,
C Zeitnitz
[show abstract]
[hide abstract]
ABSTRACT: An analog hadron calorimeter (AHCAL) prototype of 5.3 nuclear interaction lengths thickness has been constructed by members of the CALICE Collaboration. The AHCAL prototype consists of a 38-layer sandwich structure of steel plates and highly-segmented scintillator tiles that are read out by wavelength-shifting fibers coupled to SiPMs. The signal is amplified and shaped with a custom-designed ASIC. A calibration/monitoring system based on LED light was developed to monitor the SiPM gain and to measure the full SiPM response curve in order to correct for non-linearity. Ultimately, the physics goals are the study of hadron shower shapes and testing the concept of particle flow. The technical goal consists of measuring the performance and reliability of 7608 SiPMs. The AHCAL was commissioned in test beams at DESY and CERN. The entire prototype was completed in 2007 and recorded hadron showers, electron showers and muons at different energies and incident angles in test beams at CERN and Fermilab.
Journal of Instrumentation 05/2010; 5(05):P05004. · 1.87 Impact Factor
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C. Adloff,
Y Karyotakis,
J Repond,
J Yu,
G Eigen,
Y Mikami,
N K Watson,
J A Wilson,
T Goto,
G. Mavromanolakis, [......],
B. Belhorma,
M. Belmir,
S W Nam,
I H Park,
J Yang,
J-S Chai,
J T Kim, G-B Kim,
J Kang,
Y.-J. Kwon
J. Instrum. 5(2010),P05007. 04/2010;
-
A. Adare,
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
A. Al-Jamel,
K. Aoki, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: A comprehensive survey of event-by-event fluctuations of charged hadron multiplicity in relativistic heavy ions is presented. The survey covers Au+Au collisions at √sNN=62.4 and 200 GeV, and Cu+Cu collisions at √sNN=22.5,62.4, and 200 GeV. Fluctuations are measured as a function of collision centrality, transverse momentum range, and charge sign. After correcting for nondynamical fluctuations due to fluctuations in the collision geometry within a centrality bin, the remaining dynamical fluctuations expressed as the variance normalized by the mean tend to decrease with increasing centrality. The dynamical fluctuations are consistent with or below the expectation from a superposition of participant nucleon-nucleon collisions based upon p+p data, indicating that this dataset does not exhibit evidence of critical behavior in terms of the compressibility of the system. A comparison of the data with a model where hadrons are independently emitted from a number of hadron clusters suggests that the mean number of hadrons per cluster is small in heavy ion collisions.
Phys. Rev. C. 10/2008; 78(4).
-
A. Adare,
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
J. Alexander,
A. Al-Jamel,
K. Aoki, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: We present a new analysis of J/ψ production yields in deuteron-gold collisions at √sNN=200 GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler et al. [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/ψ data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (RdAu). A suppression of J/ψ in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-x gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a J/ψ (or precursor) breakup cross section is added. Breakup cross sections of σbreakup=2.8-1.4+1.7 (2.2-1.5+1.6) mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the 4.2±0.5 mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.
Phys. Rev. C. 02/2008; 77(2).
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
A. Al-Jamel,
J. Alexander,
K. Aoki,
L. Aphecetche,
R. Armendariz, [......],
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong,
H. W. vanHecke
[show abstract]
[hide abstract]
ABSTRACT: We present transverse momentum (pT) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at √sNN=200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, ν, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that yield per nucleon-nucleon collision saturates with ν for high momentum particles. We also present the charged hadron to neutral pion ratios as a function of pT.
Phys. Rev. C. 01/2008; 77(1).
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
J. Alexander,
R. Amirikas,
L. Aphecetche,
S. H. Aronson,
R. Averbeck, [......],
Y. Yang,
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
S. J. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: Measurements of neutral pion (π0) production at midrapidity in √sNN=200 GeV Au+Au collisions as a function of transverse momentum, pT, collision centrality, and angle with respect to reaction plane are presented. The data represent the final π0 results from the PHENIX experiment for the first RHIC Au+Au run at design center-of-mass energy. They include additional data obtained using the PHENIX Level-2 trigger with more than a factor of 3 increase in statistics over previously published results for pT>6 GeV/c. We evaluate the suppression in the yield of high-pT π0's relative to pointlike scaling expectations using the nuclear modification factor RAA. We present the pT dependence of RAA for nine bins in collision centrality. We separately integrate RAA over larger pT bins to show more precisely the centrality dependence of the high-pT suppression. We then evaluate the dependence of the high-pT suppression on the emission angle Δϕ of the pions with respect to event reaction plane for seven bins in collision centrality. We show that the yields of high-pT π0's vary strongly with Δϕ, consistent with prior measurements [1, 2]. We show that this variation persists in the most peripheral bin accessible in this analysis. For the peripheral bins we observe no suppression for neutral pions produced aligned with the reaction plane, whereas the yield of π0's produced perpendicular to the reaction plane is suppressed by a factor of ~2. We analyze the combined centrality and Δϕ dependence of the π0 suppression in different pT bins using different possible descriptions of parton energy loss dependence on jet path-length averages to determine whether a single geometric picture can explain the observed suppression pattern.
Phys. Rev. C. 09/2007; 76(3).
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
J. Alexander,
R. Amirikas,
L. Aphecetche,
S. H. Aronson,
R. Averbeck, [......],
Y. Yang,
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
S. J. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: Measurements of neutral pion (π0) production at midrapidity in √sNN=200 GeV Au+Au collisions as a function of transverse momentum, pT, collision centrality, and angle with respect to reaction plane are presented. The data represent the final π0 results from the PHENIX experiment for the first RHIC Au+Au run at design center-of-mass energy. They include additional data obtained using the PHENIX Level-2 trigger with more than a factor of 3 increase in statistics over previously published results for pT>6 GeV/c. We evaluate the suppression in the yield of high-pT π0's relative to pointlike scaling expectations using the nuclear modification factor RAA. We present the pT dependence of RAA for nine bins in collision centrality. We separately integrate RAA over larger pT bins to show more precisely the centrality dependence of the high-pT suppression. We then evaluate the dependence of the high-pT suppression on the emission angle Δϕ of the pions with respect to event reaction plane for seven bins in collision centrality. We show that the yields of high-pT π0's vary strongly with Δϕ, consistent with prior measurements [1, 2]. We show that this variation persists in the most peripheral bin accessible in this analysis. For the peripheral bins we observe no suppression for neutral pions produced aligned with the reaction plane, whereas the yield of π0's produced perpendicular to the reaction plane is suppressed by a factor of ~2. We analyze the combined centrality and Δϕ dependence of the π0 suppression in different pT bins using different possible descriptions of parton energy loss dependence on jet path-length averages to determine whether a single geometric picture can explain the observed suppression pattern.
Phys. Rev. C. 09/2007; 76(3).
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
J. Alexander,
R. Amirikas,
L. Aphecetche,
S. H. Aronson,
R. Averbeck, [......],
Y. Yang,
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
S. J. Zhou,
L. Zolin
[show abstract]
[hide abstract]
ABSTRACT: Longitudinal density correlations of produced matter in Au+Au collisions at √sNN=200 GeV have been measured from the inclusive charged particle distributions as a function of pseudorapidity window sizes. The extracted αξ parameter, related to the susceptibility of the density fluctuations in the long-wavelength limit, exhibits a nonmonotonic behavior as a function of the number of participant nucleons, Npart. A local maximum is seen at Npart~90, with corresponding energy density based on the Bjorken picture of εBjτ~2.4 GeV/(fm2c) with a transverse area size of 60 fm2. This behavior may suggest a critical phase boundary based on the Ginzburg-Landau framework.
Phys. Rev. C. 09/2007; 76(3).
-
A Adare,
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
H Al-Bataineh,
J Alexander,
A Al-Jamel,
K Aoki, [......],
G R Young,
I Younus,
I E Yushmanov,
W A Zajc,
O Zaudtke,
C Zhang,
S Zhou,
J Zimányi,
L Zolin,
X Zong
[show abstract]
[hide abstract]
ABSTRACT: We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from dijets in Cu+Cu and Au+Au collisions at square root sNN=62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from Delta phi=pi in central and semicentral collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.
Physical Review Letters 07/2007; 98(23):232302. · 7.37 Impact Factor
-
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
J Alexander,
R Amirikas,
L Aphecetche,
S H Aronson,
R Averbeck, [......],
Y Yang,
A Yanovich,
S Yokkaichi,
G R Young,
I E Yushmanov,
W A Zajc,
C Zhang,
S Zhou,
S J Zhou,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Emission source functions are extracted from correlation functions constructed from charged pions produced at midrapidity in Au+Au collisions at sqrt[s(NN)]=200 GeV. The source parameters extracted from these functions at low k(T) give first indications of a long tail for the pion emission source. The source extension cannot be explained solely by simple kinematic considerations. The possible role of a halo of secondary pions from resonance emissions is explored.
Physical Review Letters 04/2007; 98(13):132301. · 7.37 Impact Factor
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
J. Alexander,
A. Al-Jamel,
R. Amirikas,
K. Aoki,
L. Aphecetche, [......],
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
S. J. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: Inclusive transverse momentum spectra of η mesons in the range pT≈2–12 GeV/c have been measured at midrapidity (|η|<0.35) by the PHENIX experiment at RHIC in p+p,d+Au, and Au+Au collisions at √sNN=200 GeV. The η mesons are reconstructed through their η→γ γ channel for the three colliding systems as well as through the η→π0π+π- decay mode in p+p and d+Au collisions. The nuclear modification factor in d+Au collisions, RdAu(pT)≈1.0–1.1, suggests at most only modest pT broadening (“Cronin enhancement”). In central Au+Au reactions, the η yields are significantly suppressed, with RAuAu(pT)≈0.2. The ratio of η to π0 yields is approximately constant as a function of pT for the three colliding systems in agreement with the high-pT world average of Rη/π0≈0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies (√sNN≈3–1800 GeV) as well as, for high scaled momentum xp, in e+e- annihilations at √s=91.2 GeV. These results are consistent with a scenario where high-pT η production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (π0,η) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.
Phys. Rev. C. 02/2007; 75(2).
-
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
A Al-Jamel,
J Alexander,
K Aoki,
L Aphecetche,
R Armendariz, [......],
G R Young,
I E Yushmanov,
W A Zajc,
O Zaudtke,
C Zhang,
S Zhou,
J Zimányi,
L Zolin,
X Zong,
H W Van Hecke
[show abstract]
[hide abstract]
ABSTRACT: Cross sections for midrapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for transverse momenta of 3 < pT < 16 GeV/c. Next-to-leading order perturbative QCD (pQCD) describes the data well for pT >5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for pT >7 GeV/c.
Physical Review Letters 01/2007; 98(1):012002. · 7.37 Impact Factor
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S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
A. Al-Jamel,
J. Alexander,
K. Aoki,
L. Aphecetche,
R. Armendariz, [......],
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: The properties of jets produced in p+p collisions at √s=200 GeV are measured using the method of two-particle correlations. The trigger particle is a leading particle from a large transverse momentum jet while the associated particle comes from either the same jet or the away-side jet. Analysis of the angular width of the near-side peak in the correlation function determines the jet-fragmentation transverse momentum jT. The extracted value, √⟨jT2⟩=585±6(stat)±15(sys) MeV/c, is constant with respect to the trigger particle transverse momentum, and comparable to the previous lower √s measurements. The width of the away-side peak is shown to be a convolution of jT with the fragmentation variable, z, and the partonic transverse momentum, kT. The ⟨z⟩ is determined through a combined analysis of the measured π0 inclusive and associated spectra using jet-fragmentation functions measured in e+e- collisions. The final extracted values of kT are then determined to also be independent of the trigger particle transverse momentum, over the range measured, with value of √⟨kT2⟩=2.68±0.07(stat)±0.34(sys) GeV/c.
Phys. Rev. D. 10/2006; 74(7).
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S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
A. Al-Jamel,
J. Alexander,
K. Aoki,
L. Aphecetche,
R. Armendariz, [......],
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: PHENIX has measured the centrality dependence of midrapidity pion, kaon, and proton transverse momentum distributions in d+Au and p+p collisions at √sNN=200 GeV. The p+p data provide a reference for nuclear effects in d+Au and previously measured Au+Au collisions. Hadron production is enhanced in d+Au, relative to independent nucleon-nucleon scattering, as was observed in lower energy collisions. The nuclear modification factor for (anti)protons is larger than that for pions. The difference increases with centrality but is not sufficient to account for the abundance of baryon production observed in central Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). The centrality dependence in d+Au shows that the nuclear modification factor increases gradually with the number of collisions encountered by each participant nucleon. We also present comparisons with lower energy data as well as with parton recombination and other theoretical models of nuclear effects on particle production.
Phys. Rev. C. 08/2006; 74(2).
-
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
J Alexander,
R Amirikas,
L Aphecetche,
S H Aronson,
R Averbeck, [......],
Y Yang,
A Yanovich,
S Yokkaichi,
G R Young,
I E Yushmanov,
W A Zajc,
C Zhang,
S Zhou,
S J Zhou,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Azimuthal correlations of jet-induced high-p(T) charged hadron pairs are studied at midrapidity in Au+Au collisions at sqrt[s(NN)]=200 GeV. The distribution of jet-associated partner hadrons (1.0<p(T)<2.5 GeV/c) per trigger hadron (2.5<p(T)<4.0 GeV/c) is found to vary with collision centrality, in both shape and yield, indicating a significant effect of the nuclear collision medium on the jet fragmentation process.
Physical Review Letters 08/2006; 97(5):052301. · 7.37 Impact Factor
-
A. Adare,
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
H. Al-Bataineh,
A. Al-Jamel,
J. Alexander,
K. Aoki, [......],
G. R. Young,
I. Younus,
I. E. Yushmanov,
W. A. Zajc,
O. Zaudtke,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
Nuclear Physics A 07/2006; 774:949-953. · 1.54 Impact Factor
-
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
A Al-Jamel,
J Alexander,
K Aoki,
L Aphecetche,
R Armendariz, [......],
A Yanovich,
S Yokkaichi,
G R Young,
I E Yushmanov,
W A Zajc,
C Zhang,
S Zhou,
J Zimányi,
L Zolin,
X Zong
[show abstract]
[hide abstract]
ABSTRACT: Deuteron-gold (d+Au) collisions at the Relativistic Heavy Ion Collider provide ideal platforms for testing QCD theories in dense nuclear matter at high energy. In particular, models suggesting strong saturation effects for partons carrying small nucleon momentum fraction (x) predict modifications to jet production at forward rapidity (deuteron-going direction) in d+Au collisions. We report on two-particle azimuthal angle correlations between charged hadrons at forward/backward (deuteron/gold going direction) rapidity and charged hadrons at midrapidity in d+Au and p+p collisions at square root of sNN=200 GeV. Jet structures observed in the correlations are quantified in terms of the conditional yield and angular width of away-side partners. The kinematic region studied here samples partons in the gold nucleus with x~0.1 to ~0.01. Within this range, we find no x dependence of the jet structure in d+Au collisions.
Physical Review Letters 07/2006; 96(22):222301. · 7.37 Impact Factor
-
S S Adler,
S Afanasiev,
C Aidala,
N N Ajitanand,
Y Akiba,
J Alexander,
R Amirikas,
L Aphecetche,
S H Aronson,
R Averbeck, [......],
Y Yang,
A Yanovich,
S Yokkaichi,
G R Young,
I E Yushmanov,
W A Zajc,
C Zhang,
S Zhou,
S J Zhou,
L Zolin
[show abstract]
[hide abstract]
ABSTRACT: Inclusive transverse momentum spectra of eta mesons have been measured within p(T) = 2-10 GeV/c at midrapidity by the PHENIX experiment in Au + Au collisions at square root S(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au + Au, d + Au, and p + p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi0. The ratio of eta to pi0 spectra at high p(T) amounts to 0.40 < R(eta/pi)0 < 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e+e- collisions.
Physical Review Letters 06/2006; 96(20):202301. · 7.37 Impact Factor
-
S. S. Adler,
S. Afanasiev,
C. Aidala,
N. N. Ajitanand,
Y. Akiba,
A. Al-Jamel,
J. Alexander,
K. Aoki,
L. Aphecetche,
R. Armendariz, [......],
A. Yanovich,
S. Yokkaichi,
G. R. Young,
I. E. Yushmanov,
W. A. Zajc,
C. Zhang,
S. Zhou,
J. Zimányi,
L. Zolin,
X. Zong
[show abstract]
[hide abstract]
ABSTRACT: Dihadron correlations at high transverse momentum pT in d+Au collisions at √sNN=200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. From these correlations, we extract several structural characteristics of jets: the root-mean-squared transverse momentum of fragmenting hadrons with respect to the jet √〈jT2〉, the mean sine-squared of the azimuthal angle between the jet axes 〈sin2ϕjj〉, and the number of particles produced within the dijet that are associated with a high-pT particle (dN/dxE distributions). We observe that the fragmentation characteristics of jets in d+Au collisions are very similar to those in p+p collisions and that there is little dependence on the centrality of the d+Au collision. This is consistent with the nuclear medium having little influence on the fragmentation process. Furthermore, there is no statistically significant increase in the value of 〈sin2ϕjj〉 from p+p to d+Au collisions. This constrains the effect of multiple scattering that partons undergo in the cold nuclear medium before and after a hard collision.
Phys. Rev. C. 05/2006; 73(5).
