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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:0 パーセンタイル:100(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:6 パーセンタイル:16.18(Physics, Multidisciplinary)The PHENIX collaboration presents first measurements of low-momentum ( 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
(
,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:4 パーセンタイル:18.92(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:5 パーセンタイル:31.39(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:4 パーセンタイル:39.37(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:100(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:4 パーセンタイル:56.64(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:2 パーセンタイル:61.72(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:19 パーセンタイル:4.31(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:10 パーセンタイル:19.68(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:9 パーセンタイル:22.36(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:5 パーセンタイル:56.96(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:6 パーセンタイル:51.34(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:78.88(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:8 パーセンタイル:41.76(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.
佐甲 博之; 原田 寛之; 坂口 貴男*; 中條 達也*; 江角 晋一*; 郡司 卓*; 長谷川 勝一; Hwang, S.; 市川 裕大; 今井 憲一; et al.
Nuclear Physics A, 956, p.850 - 853, 2016/12
被引用回数:10 パーセンタイル:26.66(Physics, Nuclear)We are designing a large acceptance heavy-ion spectrometer at J-PARC based on a Toroidal magnet to measure hadrons, lepton pairs, and event-by-event fluctuations. We are also designing a closed geometry spectrometer to measure hypernuclei to study weak decays and magnetic moments. In this presentation, the preliminary version of the designed acceleration scheme, as well as the spectrometers and their expected performance and physics results are presented.
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545名*
Physical Review C, 94(6), p.064901_1 - 064901_14, 2016/12
被引用回数:41 パーセンタイル:2.98(Physics, Nuclear)The PHENIX experiment at the BNL Relativistic Heavy Ion Collider has measured second- and third-order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in Au+Au collisions at = 200 GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of
GeV/
. At low
the second-order coefficients,
, are similar to the ones observed in hadrons. Third-order coefficients,
, are nonzero and almost independent of centrality. These new results on
and
, combined with previously published results on yields, are compared to model calculations that provide yields and asymmetries in the same framework. Those models are challenged to explain simultaneously the observed large yield and large azimuthal anisotropies.
Adare, A.*; 今井 憲一; 長谷川 勝一; 永宮 正治; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他328名*
Physical Review D, 94(11), p.112008_1 - 112008_10, 2016/12
被引用回数:5 パーセンタイル:62.38(Astronomy & Astrophysics)We report the double-helicity asymmetry, , in inclusive
production at forward rapidity as a function of transverse momentum
and rapidity
. The data analyzed were taken during
GeV longitudinally polarized
collisions at the Relativistic Heavy Ion Collider in the 2013 run using the PHENIX detector. At this collision energy,
particles are predominantly produced through gluon-gluon scatterings, thus
is sensitive to the gluon polarization inside the proton. We measured
by detecting the decay daughter muon pairs
within the PHENIX muon spectrometers in the rapidity range
. In this kinematic range, we measured the
to be
. The
can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken
: one at moderate range
where recent data of jet and
double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-x region
Thus our new results could be used to further constrain the gluon polarization for
.
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397名*
Physical Review C, 94(5), p.054910_1 - 054910_18, 2016/11
被引用回数:15 パーセンタイル:16.06(Physics, Nuclear)Measurements of anisotropic flow Fourier coefficients () for inclusive charged particles and identified hadrons
,
,
, and
produced at midrapidity in Cu+Au collisions at
= 200 GeV are presented. The data were collected in 2012 by the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The particle azimuthal distributions with respect to different-order symmetry planes
, for
1, 2, and 3 are studied as a function of transverse momentum
over a broad range of collision centralities. Mass ordering, as expected from hydrodynamic flow, is observed for all three harmonics. The charged-particle results are compared with hydrodynamical and transport model calculations. We also compare these Cu+Au results with those in Cu+Cu and Au+Au collisions at the same
and find that the
and
, as a function of transverse momentum, follow a common scaling with
.
Adare, A.*; 今井 憲一; 永宮 正治; 谷田 聖; PHENIX Collaboration*; 他385名*
Physical Review C, 93(5), p.051902_1 - 051902_8, 2016/05
被引用回数:23 パーセンタイル:9.11(Physics, Nuclear)Measurements of the anisotropic flow coefficients ,
,
, and
, for identified particles (
,
, and
) at midrapidity, obtained relative to the event planes
at forward rapidities in Au + Au collisions at
200 GeV, are presented as a function of collision centrality and particle transverse momenta
. The
coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic
, a modified valence quark-number
scaling [plotting
versus transverse kinetic energies
] is observed to yield a single curve for all the measured particle species for a broad range of
. A simultaneous blast-wave model fit to the observed
coefficients and published particle spectra identifies radial flow anisotropies
and spatial eccentricities
at freeze-out. These are generally smaller than the initial-state participant-plane geometric eccentricities
as also observed in the final eccentricity from quantum interferometry measurements with respect to the event plane.