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論文

Measurements of $$e^+e^-$$ pairs from open heavy flavor in $$p+p$$ and $$d+A$$ collisions at $$sqrt{s_{NN}}$$ = 200 GeV

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

AA2017-0466.pdf:2.14MB

 被引用回数:10 パーセンタイル:19.68(Physics, Nuclear)

We report a measurement of $$e^+e^-$$ pairs from semileptonic heavy-flavor decays in $$p+p$$ collisions at $$sqrt{s_{NN}}$$ = 200 GeV. The $$e^+e^-$$ pair yield from $$bbar{b}$$ and $$cbar{c}$$ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and $$p_T$$. We used three different event generators, ${sc pythia}$, ${sc mc@nlo}$, and ${sc powheg}$, to simulate the $$e^+e^-$$ spectra from $$bbar{b}$$ and $$cbar{c}$$ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to $$4pi$$, significant differences are observed for the total cross section. These difference are less pronounced for $$bbar{b}$$ than for $$cbar{c}$$. The same model dependence was observed in already published $$d+A$$ data. The $$p+p$$ data are also directly compared with $$d+A$$ data in mass and $$p_T$$, and within the statistical accuracy no nuclear modification is seen.

論文

Beamline test of a transition-edge-sensor spectrometer in preparation for kaonic-atom measurements

橋本 直*; 谷田 聖; 他49名*

IEEE Transactions on Applied Superconductivity, 27(4), p.2100905_1 - 2100905_5, 2017/06

 被引用回数:8 パーセンタイル:36.96(Engineering, Electrical & Electronic)

We are developing a new technique to apply transition-edge sensors (TESs) to X-ray spectroscopy of exotic atoms, especially of kaonic atoms. To demonstrate the feasibility of this pioneering project, performance of a TES-based X-ray detector was evaluated in pion- and kaon-beam environments at particle accelerators. We successfully observed X-rays from pionic-carbon atoms with a resolution as good as 7 eV FWHM at 6 keV. Also at a kaon beamline, we confirmed that the TES spectrometer will be able to achieve our resolution goal, 6 eV, in our first scientific campaign to measure X-rays from kaonic-helium atoms.

論文

Systematic study of charged-pion and kaon femtoscopy in Au + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他493名*

Physical Review C, 92(3), p.034914_1 - 034914_21, 2015/09

AA2015-0712.pdf:1.48MB

 被引用回数:17 パーセンタイル:16.73(Physics, Nuclear)

We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at $$sqrt{s_{NN}}$$ = 200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthal angle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations.

口頭

TES application to kaonic atom X-ray spectroscopy in a charged-particle beamline

橋本 直*; 谷田 聖; 他49名*

no journal, , 

We are developing a new technique to study the strong interaction between a hadron and an atomic nucleus: high-resolution TES-based X-ray spectroscopy of hadronic atoms. The strong interaction induces a shift and broadening of the atomic energy levels from their purely electromagnetic values. Thus, precise measurements of the X-ray-emission lines of a hadronic atom can reveal the hadron-nucleus strong interaction at zero kinetic energy. Presently, we are preparing to measure the $$3d$$-$$2p$$ X-ray lines of kaonic helium-3 and helium-4 (6.2 keV and 6.4 keV, respectively) at the Japan Proton Accelerator Research Complex (J-PARC; Tokai, Japan). If we determined the strong-force shift in the helium 2p orbital to a precision of 0.2 eV, we could distinguish between the two leading antikaon-nucleus strong-interaction models. Here, we plan to use a 240-pixel TES array of about 23 mm$$^2$$ collecting area with 4 $$mu$$m thick Bi absorbers. Our project represents the first attempt to use a TES-based X-ray spectrometer in a charged-particle beamline, and we have identified some challenges: (1) energy resolution is deteriorated by charged-particle passages; (2) a continuum background in the X-ray spectrum is generated by charged particles; (3) the science X-ray yield is expected to be very low, at 200 counts per week for the kaonic-helium-atom experiment. Here we present the status of our project.

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