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Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*
Physical Review C, 102(6), p.064905_1 - 064905_13, 2020/12
被引用回数:2 パーセンタイル:34.22(Physics, Nuclear)The PHENIX experiment at the Relativistic Heavy Ion Collider measured and
mesons at midrapidity in U
U collisions at
GeV in a wide transverse momentum range. Measurements were performed in the
decay modes. A strong suppression of
and
meson production at high transverse momentum was observed in central U
U collisions relative to binary scaled
results. Yields of
and
mesons measured in U
U collisions show similar suppression pattern to the ones measured in Au
Au collisions at
GeV for similar numbers of participant nucleons. The
/
ratios do not show dependence on centrality or transverse momentum, and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and
collisions.
Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他572名*
Physical Review C, 102(5), p.054910_1 - 054910_11, 2020/11
被引用回数:0 パーセンタイル:0.02(Physics, Nuclear)We present direct photon-hadron correlations in 200 GeV/A AuAu,
Au and
collisions, for direct photon
from 5 - 12 GeV/
, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in
Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in Au
Au compared to
and
Au. As the momentum fraction decreases, the yield of hadrons in Au
Au increases to an excess over the yield in
collisions. The excess is at large angles and at low hadron
and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.
Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他344名*
Physical Review D, 102(9), p.092002_1 - 092002_14, 2020/11
被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)The cross section of bottom quark-antiquark () production in
collisions at
GeV is measured with the PHENIX detector at the Relativistic Heavy Ion Collider. The results are based on the yield of high mass, like-sign muon pairs measured within the PHENIX muon arm acceptance (
). The
signal is extracted from like-sign dimuons by utilizing the unique properties of neutral
meson oscillation. We report a differential cross section of
nb for like-sign muons in the rapidity and
ranges
and
GeV/
, and dimuon mass of 5 - 10 GeV/
. The extrapolated total cross section at this energy for
production is
b. The total cross section is compared to a perturbative quantum chromodynamics calculation and is consistent within uncertainties. The azimuthal opening angle between muon pairs from
decays and their
distributions are compared to distributions generated using
, which includes next-to-leading order processes. The azimuthal correlations and pair
distribution are not very well described by
calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.
Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他344名*
Physical Review D, 102(7), p.072008_1 - 072008_13, 2020/10
被引用回数:2 パーセンタイル:21.58(Astronomy & Astrophysics)The PHENIX experiment has measured the spin alignment for inclusive decays in
collisions at
GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of
GeV/
. The results are consistent with a previous one-dimensional analysis at midrapidity at
GeV. The transverse-momentum-dependent cross section for midrapidity
production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on
.
Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他354名*
Physical Review D, 102(3), p.032001_1 - 032001_9, 2020/08
被引用回数:2 パーセンタイル:21.58(Astronomy & Astrophysics)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, , for charged pions at midrapidity (
) in longitudinally polarized
collisions at
GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction
range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at
GeV, which show a nonzero positive contribution of gluon spin to the proton spin.
Acharya, U. A.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他353名*
Physical Review D, 101(5), p.052006_1 - 052006_13, 2020/03
被引用回数:4 パーセンタイル:31.53(Astronomy & Astrophysics)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive and cross-section ratio of
to
at forward rapidity in
collisions at
GeV via the dimuon decay channel. Comparison is made to inclusive
cross sections measured at
GeV and 2.76 - 13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-
gluons in the proton at low transverse momentum (
) and to next-to-leading order nonrelativistic QCD calculations for the rest of the
range. These calculations overestimate the data at low
. While consistent with the data within uncertainties above
GeV/
, the calculations are systematically below the data. The total cross section times the branching ratio is BR
GeV/
) = 54.3
0.5 (stat)
5.5 (syst) nb.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他666名*
Physical Review Letters, 123(2), p.022301_1 - 022301_10, 2019/07
被引用回数:20 パーセンタイル:84.25(Physics, Multidisciplinary)The PHENIX collaboration presents first measurements of low-momentum (0.4 3 GeV/
) direct-photon yields from Au
Au collisions at
= 39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au
Au collisions at
= 200. Analyzing the photon yield as a function of the experimental observable
reveals that the low-momentum (
1 GeV/
) direct-photon yield
is a smooth function of
and can be well described as proportional to
with
1.25. This new scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and Large Hadron Collider, for centrality selected samples, as well as for different,
collision systems. At a given beam energy the scaling also holds for high
(
5 GeV/
) but when results from different collision energies are compared, an additional
-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他451名*
Physical Review C, 99(5), p.054903_1 - 054903_29, 2019/05
被引用回数:11 パーセンタイル:78.79(Physics, Nuclear)We present measurements of azimuthal correlations of charged hadron pairs in GeV Au
Au collisions after subtracting an underlying event using a model that includes higher-order azimuthal anisotropy
,
, and
. After subtraction, the away-side (
of the highest transverse-momentum trigger (
GeV/
) correlations is suppressed compared to that of correlations measured in
collisions. At the lowest associated particle
, the away-side shape and yield are modified. These observations are consistent with the scenario of radiative-jet energy loss. For the lowest-
trigger correlations, an away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle
. The angular correlations show an asymmetry when selecting the sign of the trigger-particle azimuthal angle with respect to the
event plane. This asymmetry and the measured suppression of the pair yield out of plane is consistent with a path-length-dependent energy loss. No
dependence can be resolved within experimental uncertainties.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他448名*
Physical Review C, 98(5), p.054902_1 - 054902_11, 2018/11
被引用回数:11 パーセンタイル:73.83(Physics, Nuclear)We have measured direct photons for GeV/
in minimum bias and 0% - 40% most central events at midrapidity for Cu
Cu collisions at
GeV. The
contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the
mass distribution. A clear enhancement of photons over the binary scaled
fit is observed for
GeV/
in Cu
Cu data. The
spectra are consistent with the Au
Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the
baseline are 285
53(stat)
57(syst)~MeV/
and 333
72(stat)
45(syst)~MeV/
for minimum bias and 0% - 40% most central events, respectively. The rapidity density,
, of photons demonstrates the same power law as a function of
observed in Au
Au at the same collision energy.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*
Physical Review C, 98(5), p.054903_1 - 054903_11, 2018/11
被引用回数:8 パーセンタイル:63.75(Physics, Nuclear)Production of and
mesons has been measured at midrapidity in Cu
Au collisions at
=200 GeV. Measurements were performed in
decay channel in the 1(2)-20 GeV/
transverse momentum range. A strong suppression is observed for
and
meson production at high transverse momentum in central Cu
Au collisions relative to the
results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au
Au with comparable nuclear overlap. The
ratio measured as a function of transverse momentum is consistent with
-scaling parameterization down to
2 GeV/
, its asymptotic value is constant and consistent with Au
Au and
and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in
collisions in a range of collision energies
3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu
Cu collisions either does not affect the jet fragmentation into light mesons or it affects the
and
the same way.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他351名*
Physical Review D, 98(9), p.092006_1 - 092006_13, 2018/11
被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section of (1020) meson production at forward rapidity in
collisions at
510 GeV via the dimuon decay channel. The integrated cross section in the rapidity and
ranges
and
GeV/
is
~mb. The energy dependence of
(
;
GeV/
) is studied using the PHENIX measurements at
200 and 510 GeV and the Large-Hadron-Collider measurements at
2.76 and 7 TeV. The experimental results are compared to various event generator predictions (pythia6, pythia8, phojet, ampt, epos3, and epos-lhc).
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他423名*
Physical Review D, 98(3), p.032007_1 - 032007_14, 2018/08
被引用回数:11 パーセンタイル:56.97(Astronomy & Astrophysics)We have measured the cross section and single spin asymmetries from forward production in longitudinally polarized
collisions at
GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. The cross sections are consistent with previous measurements at this collision energy, while the most forward and backward longitudinal single spin asymmetries provide new insights into the sea quark helicities in the proton. The charge of the
bosons provides a natural flavor separation of the participating partons.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他468名*
Physical Review C, 98(1), p.014912_1 - 014912_16, 2018/07
被引用回数:6 パーセンタイル:53.84(Physics, Nuclear)We present measurements of two-particle angular correlations between high-transverse-momentum ( GeV/
)
observed at midrapidity (
) and particles produced either at forward (
) or backward (
) rapidity in
Au and
collisions at
GeV. The azimuthal angle correlations for particle pairs with this large rapidity gap in the Au-going direction exhibit a ridge-like structure that persists up to
GeV/
and which strongly depends on collision centrality, which is a similar characteristic to the hydrodynamical particle flow in A+A collisions. The ridge-like structure is absent in the
-going direction as well as in
collisions, in the transverse-momentum range studied. The results indicate that the ridge-like structure is shifted in the Au-going direction toward more central collisions, similar to the charged-particle pseudorapidity distributions.
Adare, A.*; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他448名*
Physical Review C, 97(6), p.064911_1 - 064911_22, 2018/06
被引用回数:24 パーセンタイル:90.99(Physics, Nuclear)We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality GeV Au
Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from L
vy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter
, the L
vy index of stability
and the L
vy length scale parameter
as a function of average transverse mass of the pair
. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same L
vy-stable source functions. The
measurements indicate a decrease of the strength of the correlations at low
. The L
vy length scale parameter
decreases with increasing
, following a hydrodynamically predicted type of scaling behavior. The values of the L
vy index of stability
are found to be significantly lower than the Gaussian case of
, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他497名*
Physical Review C, 96(2), p.024907_1 - 024907_19, 2017/08
被引用回数:11 パーセンタイル:70.12(Physics, Nuclear)We report a measurement of pairs from semileptonic heavy-flavor decays in
collisions at
= 200 GeV. The
pair yield from
and
is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and
. We used three different event generators,
,
, and
, to simulate the
spectra from
and
production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to
, significant differences are observed for the total cross section. These difference are less pronounced for
than for
. The same model dependence was observed in already published
data. The
data are also directly compared with
data in mass and
, and within the statistical accuracy no nuclear modification is seen.
本多 良太郎*; 長谷川 勝一; 早川 修平; 細見 健二; 市川 裕大; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 杉村 仁志; et al.
Physical Review C, 96(1), p.014005_1 - 014005_23, 2017/07
被引用回数:13 パーセンタイル:75.45(Physics, Nuclear)We searched for the bound state of the neutron-rich -hypernucleus
H, using the
Li
double charge-exchange reaction at a
beam momentum of 1.2 GeV/
at J-PARC. A total of
was driven onto a
Li target of 3.5 g/cm
thickness. No event was observed below the bound threshold, i.e., the mass of
H+
, in the missing-mass spectrum of the
Li
reaction in the
angular range. Furthermore, no event was found up to 2.8 MeV/c
above the bound threshold.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他431名*
Physical Review D, 95(11), p.112001_1 - 112001_15, 2017/06
被引用回数:13 パーセンタイル:59.43(Astronomy & Astrophysics)The cross section and transverse single-spin asymmetries of and
from open heavy-flavor decays in polarized
collisions at
= 200 GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at
= 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (
) over the transverse momentum range of
GeV/
for the cross section and
GeV/
for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.
Aidala, C.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他425名*
Physical Review D, 95(9), p.092002_1 - 092002_18, 2017/05
被引用回数:7 パーセンタイル:40.51(Astronomy & Astrophysics)We report the first measurement of the fraction of mesons coming from
-meson decay (
) in
collisions at
GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of
due to
-meson decays from prompt
. The measured value of
is
for
with transverse momenta
GeV/
and rapidity
. The measured fraction
at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-to-leading-logarithm and color-evaporation-model predictions. The
cross section per unit rapidity
extracted from the obtained
and the PHENIX inclusive
cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean
hadron rapidity
in 510 GeV
collisions, is
b. It is consistent with the fixed-order-next-to-leading-logarithm calculations.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他389名*
Physical Review D, 95(9), p.092003_1 - 092003_13, 2017/05
被引用回数:2 パーセンタイル:15.09(Astronomy & Astrophysics)We report the first measurement of the full angular distribution for inclusive decays in
collisions at
GeV. The measurements are made for
transverse momentum
GeV/
and rapidity
in the Helicity, Collins-Soper, and Gottfried-Jackson reference frames. In all frames the polar coefficient
is strongly negative at low
and becomes close to zero at high
, while the azimuthal coefficient
is close to zero at low
, and becomes slightly negative at higher
. The frame-independent coefficient
is strongly negative at all
in all frames. The data are compared to the theoretical predictions provided by nonrelativistic quantum chromodynamics models.
Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他462名*
Physical Review D, 95(7), p.072002_1 - 072002_19, 2017/04
被引用回数:11 パーセンタイル:54.06(Astronomy & Astrophysics)Dihadron and isolated direct photon-hadron angular correlations are measured in collisions at
= 510 GeV. Correlations of charged hadrons of
GeV/
with
mesons of
GeV/
or isolated direct photons of
GeV/
are used to study nonperturbative effects generated by initial-state partonic transverse momentum and final-state transverse momentum from fragmentation. The nonperturbative behavior is characterized by measuring the out-of-plane transverse momentum component
perpendicular to the axis of the trigger particle, which is the high-
direct photon or
. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (
). The Gaussian widths and root mean square of
are reported as a function of the interaction hard scale
to investigate possible transverse-momentum-dependent evolution differences between the
-
and direct photon-
correlations and factorization breaking effects. The widths are found to decrease with
, which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in
collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.