Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
mesons in proton-nucleus reactions from a transport approachGubler, P.; 市川 真也; Song, T.*; Bratkovskaya, E.*
Physical Review C, 111(3), p.034908_1 - 034908_12, 2025/03
被引用回数：1 パーセンタイル：90.19(Physics, Nuclear)Production and in-medium modification of hidden strange mesons are studied in proton-nucleus reactions: p+C, p+Cu, and p+Pb at 12 GeV/c, partially measured by the KEK E325 Collaboration via the dilepton decay mode. This work is based on the off-shell microscopic parton-hadron-string dynamics transport approach, and especially makes it possible to simulate in-medium off-shell dynamics of the meson in the reactions studied. Different in-medium scenarios for the modification of the meson spectral function in nuclear matter are investigated: (i) dropping pole mass, (ii) collisional broadening, and (iii) simultaneous dropping pole mass and collisional broadening. Even though the meson production in p+A reactions occurs only at densities around or below normal nuclear matter density 
, we find visible modifications of the generated dilepton spectra for the in-medium scenarios compared to the vacuum distribution.
correlation functionAbreu, L. M.*; Gubler, P.; Khemchandani, K. P.*; Mart
nez Torres, A.*; 保坂 淳
Physics Letters B, 860, p.139175_1 - 139175_7, 2025/01
被引用回数：3 パーセンタイル：52.60(Astronomy & Astrophysics)The femtoscopic correlation function is studied within a hadronic effective Lagrangian approach with coupled channels, based on hidden local symmetry. The results are compared with the data recently reported by the ALICE collaboration. We find that the correlation function has very different features for the system in the spin 1/2 and 3/2 configurations, with the spin-averaged combination matching well with the experimental data. A strong attraction, leading to the formation of a bound state or a very prominent cusp is found in the spin 3/2 case. The correlation function for spin 1/2, on the other hand, is strongly impacted by the negative parity 
*(1895) nucleon resonance.
, 
, 
and 
mesons through their angular-dependent two-body decay modesPark, I. W.*; 佐甲 博之; 青木 和也*; Gubler, P.; Lee, S. H.*
Journal of Subatomic Particles and Cosmology (Internet), 1-2, p.100014_1 - 100014_11, 2024/11
The mass shift a spin-1 particle moving in the nuclear medium will depend on its polarization direction. To study polarization-independent mass shifts in the medium, we explore methods to isolate each polarization direction of spin-1 mesons through the angular-dependent two-body decay modes. Specifically, we study 
, 
, 
, 
and 
(
) decays. Concerning and mesons, since both particles have vacuum widths smaller than 100 MeV, they are ideal candidates for experimentally measuring chiral partners. The simultaneous observation of mass shifts of these chiral partners would provide valuable insights into the contribution of chiral symmetry breaking to the generation of hadron masses.
Kumar, A.*; Yang, D.-L.*; Gubler, P.
Physical Review D, 109(5), p.054038_1 - 054038_16, 2024/03
被引用回数：11 パーセンタイル：95.41(Astronomy & Astrophysics)Starting with the polarization dependent Wigner function of vector mesons, we derive an expression for the 00-component (
) of spin density matrix in terms of the second order gradients of the vector meson distribution functions. We further apply a thermal model to analyze the transverse momentum and the azimuthal angle dependence of for and 
mesons resulting from distribution gradients in Au-Au collisions with 
GeV at midrapidity. Our results for the transverse momentum dependence indicate that the deviations of from 1/3 as the signal for spin alignment are greatly enhanced at large transverse momenta and have a strong centrality dependence while analysis of the azimuthal angle 
dependence suggest that such deviations have a 
structure with opposite sign for and . Our finding may be considered as a baseline for probing spin-alignment mechanisms beyond hydrodynamic gradients.
meson through dilepton and kaon decaysPark, I. W.*; 佐甲 博之; 青木 和也*; Gubler, P.; Lee, S. H.*
Physical Review D, 107(7), p.074033_1 - 074033_9, 2023/04
被引用回数：10 パーセンタイル：79.18(Astronomy & Astrophysics)Angular distributions of meson decay amplitudes of 
and 
channels are computed using both specific interaction Lagrangians and simple arguments relying on angular momentum conservation. Based on the obtained results, we assess methods to experimentally disentangle the longitudinal and transverse polarization modes of the meson and discuss advantages and disadvantages of employing either the leptonic or hadronic decay modes for this task.
meson with finite momentum in a dense mediumKim, H.-J.*; Gubler, P.
Physics Letters B, 805, p.135412_1 - 135412_8, 2020/06
被引用回数：21 パーセンタイル：87.95(Astronomy & Astrophysics)QCD和則を利用し、核物質におけるメソンの分散関係を調べる。敗れたLorentz対称性により、有限密度中ではベクター粒子のlongitudinal及びtransverseモードが異なる振る舞いを示しえる。次元6までの可能な演算子及びそのWilson係数をすべて用い、様々な密度及び運動量におけるメソンの分散関係を解析する。その結果、longitudinal及びtransverseモードが逆の振る舞いを示すことが分かった。実際、運動量1GeVでは、longitudinalモードでは質量が5MeVほど下り、transverseモードでは7MeVほど上がることが分かった。longitudinal及びtransverseモードを区別しない実験では、この現象が二つの分離されたピークとして観測される可能性がある。
Gubler, P.; Kim, H. J.*; Lee, S. H.*
no journal, ,
有限運動量を持つ核物質中のphiメソンの振る舞いについての最近の研究の進捗状況について報告する。J-PARCのE16実験との関連についても議論する。
Gubler, P.
no journal, ,
We present recent results of numerical simulations of the 12 GeV pA reactions probed at the KEK E325 experiment using a transport approach. Furthermore, we discuss how the simulation results can be used to interpret the experimental data in terms of the modification of the phi meson at finite density. Finally, we will give an outlook to the presently ongoing J-PARC E16 experiment.
decaysGubler, P.
no journal, ,
While the meson vacuum properties, such as mass and width, are well known, it is not clear how these properties will change once it is put in a dense environment such as nuclear matter. Theoretically, many works have been conducted with the aim of studying the meson in nuclear matter. Connecting theoretical results with experimental measurements is, however, not a trivial task, as the meson in nuclear matter is usually produced in relatively high-energy pA reactions, which are generally non-equilibrium processes. In this presentation I will report on an ongoing project, attempting to simulate pA reactions in which the meson is produced in nuclei, making use of a transport approach. Results of simulations of 12 GeV/30 GeV p+C and p+Cu reactions will be presented and comparisons between obtained dilepton spectra and experimental data of the E325 experiment at KEK will be made.
meson in nuclear matter; Interpreting the E325 data in a transport approachGubler, P.
no journal, ,
We present recent results of numerical simulations of the 12 GeV pA reactions probed at the KEK E325 experiment using a transport approach. Furthermore, we discuss how the simulation results can be used to interpret the experimental data in terms of the modification of the phi meson at finite density.
Gubler, P.
no journal, ,
本講演の前半では核物質中でのカイラル対称性の部分的回復の現状を概観する。後半では自分がここ数年取り組んでいる核物質中のメソンの振る舞いに関する研究を紹介し、特にJ-PARCのE16実験との関連を議論する。
modification with high-statistics decay measurements in 30-GeV proton-nucleus collisions佐甲 博之
no journal, ,
meson is a good probe to explore mass modification inside the nucleus due to partial restoration of chiral condensate with its narrow width. In particular, modification of meson mass is sensitive to strange quark condensate. J-PARC E88 is proposed as an experiment to study modification of meson mass inside nuclei in p+A collisions. Complementary to 
decay measurements at J-PARC E16, E88 will measure high-statistics 
decays of 
M in p+C, p+Cu, and p+Pb. Utilizing high-statistics data, we will measure the momentum dependence of mass modification (dispersion relation), which is used to extrapolate to zero momentum to evaluate strange quark condensate. Also, we will measure the dispersion relations for longitudinal and transverse polarized 's with 
decay angle, which are predicted to be different in QCD sum rules. In this presentation, we will discuss physics goals, the experimental design, and the preparation status.
