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論文

Measurements of $$q^2$$ moments of inclusive $$B rightarrow X_c ell^+ nu_{ell}$$ decays with hadronic tagging

van Tonder, R.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review D, 104(11), p.112011_1 - 112011_32, 2021/12

https://doi.org/10.1103/PhysRevD.104.112011
 被引用回数：10 パーセンタイル：65.5(Astronomy & Astrophysics)

We present the measurement of the first to fourth order moments of the four-momentum transfer squared, $$q^2$$, of inclusive $$B rightarrow X_c ell^+ nu_{ell}$$ decays using the full Belle data set of 711 $$mathrm{fb}^{-1}$$ of integrated luminosity at the $$Upsilon(4S)$$ resonance where $$ell = e, mu$$. The determination of these moments and their systematic uncertainties open new pathways to determine the absolute value of the CKM matrix element $$V_{cb}$$ using a reduced set of matrix elements of the heavy quark expansion. In order to identify and reconstruct the $$X_c$$ system, we reconstruct one of the two $$B$$-mesons using machine learning techniques in fully hadronic decay modes. The moments are measured with progressively increasing threshold selections on $$q^2$$ starting with a lower value of 3.0 $$mathrm{GeV}^2$$ in steps of 0.5 $$mathrm{GeV}^2$$ up to a value of 10.0 $$mathrm{GeV}^2$$. The measured moments are further unfolded, correcting for reconstruction and selection effects as well as QED final state radiation. We report the moments separately for electron and muon final states and observe no lepton flavor universality violating effects.

論文

Measurement of the masses and widths of the $$Sigma_c(2455)^+$$ and $$Sigma_c(2520)^+$$ baryons

Yelton, J.*; 谷田 聖; Belle Collaboration*; 他205名*

Physical Review D, 104(5), p.052003_1 - 052003_8, 2021/09

https://doi.org/10.1103/PhysRevD.104.052003
 被引用回数：4 パーセンタイル：37.94(Astronomy & Astrophysics)

Using 980 $${rm fb}^{-1}$$ of data ${collected}$ with the Belle detector operating at the KEKB asymmetric-energy $$e^+e^-$$ collider, we report the measurements of the masses, and the first measurements of the instrinsic widths, of the $$Sigma_c(2455)^+$$ and $$Sigma_c(2520)^+$$ charmed baryons. We find $$M(Sigma_c(2455)^+)-M(Lambda_c^+) = 166.17pm 0.05^{+0.16}_{-0.07} {rm MeV}/c^2$$, $$Gamma(Sigma_c(2455)^+) = 2.3 pm 0.3 pm 0.3 {rm MeV/c^2}$$, $$M(Sigma_c(2520)^+)-M(Lambda_c^+) = 230.9 pm 0.5 ^{+0.5}_{-0.1} {rm MeV}/c^2$$, and $$Gamma(Sigma_c(2520)^+) = 17.2^{+2.3 +3.1}_{-2.1 -0.7} {rm MeV}/c^2$$, where the uncertainties are statistical and systematic, respectively. These measurements can be used to test models of the underlying quark structure of the $$Sigma_c$$ states.

論文

Search for the $$eta_{c2}(1D)$$ in $$e^+e^-togammaeta_{c2}(1D)$$ at $$sqrt{s}$$ near 10.6 GeV at Belle

Jia, S.*; 谷田 聖; Belle Collaboration*; 他200名*

Physical Review D, 104(1), p.012012_1 - 012012_9, 2021/07

https://doi.org/10.1103/PhysRevD.104.012012
 被引用回数：0 パーセンタイル：0.01(Astronomy & Astrophysics)

For the first time we search for the $$eta_{c2}(1D)$$ in $$e^+e^-togammaeta_{c2}(1D)$$ at $$sqrt{s}$$ = 10.52, 10.58, and 10.867 GeV with data samples of 89.5 fb$$^{-1}$$, 711 fb$$^{-1}$$, and 121.4 fb$$^{-1}$$, respectively, accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant $$eta_{c2}(1D)$$ signal is observed in the mass range between 3.8 and 3.88 GeV/$$c^2$$. The upper limit at 90% confidence level on the product of the Born cross section for $$e^+e^- to gammaeta_{c2}(1D)$$ and branching fraction for $$eta_{c2}(1D)to gamma h_c(1P)$$ is determined to be $$sigma(e^+e^- to gammaeta_{c2}(1D)){cal B}(eta_{c2}(1D)to gamma h_c(1P))$$ $$<$$ 4.9 fb at $$sqrt{s}$$ near 10.6 GeV.

論文

Measurement of branching fractions and $$CP$$ asymmetries for $$D_s^{+} rightarrow K^+ (eta, pi^0) $$ and $$D_s^{+} rightarrow pi^+ (eta, pi^0)$$ decays at Belle

Guan, Y.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review D, 103(11), p.112005_1 - 112005_11, 2021/06

https://doi.org/10.1103/PhysRevD.103.112005
 被引用回数：5 パーセンタイル：45.23(Astronomy & Astrophysics)

We report measurements of the branching fractions and $$CP$$ asymmetries for $$D_s^{+} rightarrow K^{+} eta $$, $$D_s^{+} rightarrow K^{+} pi^0 $$, and $$D_s^{+} rightarrow pi^{+} eta $$ decays, and the branching fraction for $$D_s^{+} rightarrow pi^{+} pi^0$$. Our results are based on a data sample corresponding to an integrated luminosity of 921 fb$$^{-1}$$ collected by the Belle detector at the KEKB $$e^+e^-$$ asymmetric-energy collider. Our measurements of $$CP$$ asymmetries in these decays are the most precise to-date; no evidence for $$CP$$ violation is found.

論文

First determination of the spin and parity of the charmed-strange baryon $$Xi_{c}(2970)^+$$

Moon, T. J.*; 谷田 聖; Belle Collaboration*; 他203名*

Physical Review D, 103(11), p.L111101_1 - L111101_9, 2021/06

https://doi.org/10.1103/PhysRevD.103.L111101
 被引用回数：18 パーセンタイル：85.82(Astronomy & Astrophysics)

We report results from a study of the spin and parity of $$Xi_{c}(2970)^+$$ using a $$980~mathrm{fb^{-1}}$$ data sample collected by the Belle detector at the KEKB asymmetric-energy $$e^{+}e^{-}$$ collider. The decay angle distributions in the chain $$Xi_{c}(2970)^+ to Xi_c(2645)^{0}pi^{+} to Xi_c^{+}pi^{-}pi^{+}$$ are analyzed to determine the spin of this charmed-strange baryon. The angular distributions strongly favor the $$Xi_{c}(2970)^+$$ spin $$J =1/2$$ over $$3/2$$ or $$5/2$$, under an assumption that the lowest partial wave dominates in the decay. We also measure the ratio of $$Xi_{c}(2970)^+$$ decay branching fractions $$R={mathcal{B}[ Xi_{c}(2970)^+ to Xi_c(2645)^{0}pi^{+} ]} $$ / $${ mathcal{B}[ Xi_{c}(2970)^+ to Xi_c^{prime0}pi^{+} ]} $$ =1.67 $$pm 0.29mathrm{(stat.)}^{ +0.15}_{-0.09}mathrm{(syst.)} $$ $$pm 0.25mathrm{(IS)}$$, where the last uncertainty is due to possible isospin-symmetry-breaking effects. This $$R$$ value favors the spin-parity $$J^P=1/2^+$$ with the spin of the light-quark degrees of freedom $$s_{l}=0$$. This is the first determination of the spin and parity of a charmed-strange baryon.

論文

Measurements of the branching fractions of $$Lambda_c^+ to p eta$$ and $$Lambda_c^+ to p pi^0$$ decays at Belle

Li, S. X.*; 谷田 聖; Belle Collaboration*; 他203名*

Physical Review D, 103(7), p.072004_1 - 072004_9, 2021/04

https://doi.org/10.1103/PhysRevD.103.072004
 被引用回数：9 パーセンタイル：65.5(Astronomy & Astrophysics)

We report measurements of the branching fractions of singly Cabibbo-suppressed decays $$Lambda_c^+ to p eta$$ and $$Lambda_c^+ to p pi^0$$ using the full Belle data sample corresponding to an integrated luminosity of 980.6 $$rm fb^{-1}$$. The data were collected by the Belle detector at the KEKB $$e^{+}$$$$e^{-}$$ asymmetric-energy collider. A clear $$Lambda_c^+$$ signal is seen in the invariant mass distribution of $$p eta$$. The signal yield of the $$Lambda_c^+ to p eta$$ process is $$7734 pm 263$$; from this, we measure the ratio of branching fractions $${cal B}(Lambda_c^+ to p eta)/{cal B}(Lambda_c^+ to p K^- pi^+) = (2.258 pm 0. 077(rm stat.) pm 0.136(rm syst.))times 10^{-2}$$, from which we infer the branching fraction $${cal B}(Lambda_c^+ to p eta) = (1.42 pm 0.05(rm stat.) pm 0.11(rm syst.)) times 10^{-3}$$. In addition, no significant signal for $$Lambda_c^+ to p pi^0$$ is found so an upper limit on the branching fraction of $${cal B}(Lambda_c^+ to p pi^0) < 8.0 times 10^{-5}$$ at 90% credibility level is set, more than three times better than the best current upper limit.

論文

Measurement of branching fractions of $$Lambda_{c}^{+} rightarrow etaLambdapi^{+}$$, $$eta Sigma^{0} pi^{+}$$, $$Lambda(1670) pi^{+}$$, and $$eta Sigma(1385)^{+}$$

Lee, J. Y.*; 谷田 聖; Belle Collaboration*; 他201名*

Physical Review D, 103(5), p.052005_1 - 052005_12, 2021/03

https://doi.org/10.1103/PhysRevD.103.052005
 被引用回数：6 パーセンタイル：51.62(Astronomy & Astrophysics)

We report branching fraction measurements of four decay modes of the $$Lambda_{c}^{+}$$ baryon, each of which includes an $$eta$$ meson and a $$Lambda$$ baryon in the final state, and all of which are measured relative to the $$Lambda_{c}^{+} rightarrow p K^{-} pi^{+}$$ decay mode. The results are based on a $$980~mathrm{fb^{-1}}$$ data sample collected by the Belle detector at the KEKB asymmetric-energy $$e^{+}e^{-}$$ collider. Two decays, $$eta Sigma^{0} pi^{+}$$ and $$Lambda(1670) pi^{+}$$, are observed for the first time, while the measurements of the other decay modes, $$Lambda_{c}^{+} rightarrow etaLambdapi^{+}$$ and $$etaSigma(1385)^{+}$$, are more precise than those made previously. We obtain $$mathcal{B}(Lambda_{c}^{+} rightarrow eta Lambda pi^{+})$$/$$mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})$$ = $$0.293 pm 0.003 pm 0.014$$, $$mathcal{B}(Lambda_{c}^{+} rightarrow eta Sigma^{0} pi^{+})$$/$$mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})$$ = $$0.120 pm 0.006 pm 0.006$$, $$mathcal{B}(Lambda_{c}^{+} rightarrow Lambda(1670) pi^{+}) times mathcal{B}(Lambda(1670) rightarrow etaLambda) $$/$$mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-} pi^{+})$$ = $$(5.54 pm 0.29 pm 0.73) times 10^{-2}$$, and $$mathcal{B}(Lambda_{c}^{+} rightarrow eta Sigma(1385)^{+}) $$/$$mathcal{B}(Lambda_{c}^{+} rightarrow p K^{-}pi^{+})$$ = $$0.192 pm 0.006 pm 0.016$$. The mass and width of the $$Lambda(1670)$$ are also precisely determined to be $$1674.3 pm 0.8 pm 4.9~{rm MeV}/c^{2}$$ and $$36.1 pm 2.4 pm 4.8~{rm MeV}$$, respectively, where the uncertainties are statistical and systematic, respectively.

論文

Measurement of time-dependent $$CP$$ violation parameters in $$B^{0} to K^{0}_{S}K^{0}_{S}K^{0}_{S}$$ decays at Belle

Kang, K. H.*; 谷田 聖; Belle Collaboration*; 他204名*

Physical Review D, 103(3), p.032003_1 - 032003_8, 2021/02

https://doi.org/10.1103/PhysRevD.103.032003
 被引用回数：2 パーセンタイル：20.63(Astronomy & Astrophysics)

We measure the time-dependent $$C!P$$ violation parameters in $$B^{0} to K^{0}_{S}K^{0}_{S}K^{0}_{S}$$ decays using $$772 times 10^6$$ $$B {mkern 1.5muoverline{mkern-1.5mu B mkern-0.1mu}mkern 0.1mu}$$ pairs collected at the $$Upsilon (4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider. The obtained mixing-induced and direct $$C!P$$ asymmetries are $$-0.71 pm 0.23~{rm(stat)} pm 0.05~{rm(syst)}$$ and $$0.12 pm 0.16~{rm(stat)} pm 0.05~{rm(syst)}$$, respectively. These values are consistent with the Standard Model predictions. The significance of $$C!P$$ violation differs from zero by 2.5 standard deviations.

論文

Search for a doubly charged $$DDK$$ bound state in $$Upsilon(1S, 2S)$$ inclusive decays and via direct production in $$e^+e^-$$ collisions at $$sqrt{s}$$ = 10.520, 10.580, and 10.867 GeV

Li, Y.*; 谷田 聖; Belle Collaboration*; 他205名*

Physical Review D, 102(11), p.112001_1 - 112001_14, 2020/12

https://doi.org/10.1103/PhysRevD.102.112001
 被引用回数：5 パーセンタイル：36.79(Astronomy & Astrophysics)

We report the results of a first search for a doubly-charged $$DDK$$ bound state, denoted the $$R^{++}$$, in $$Upsilon(1S)$$ and $$Upsilon(2S)$$ inclusive decays and via direct production in $$e^+e^-$$ collisions at $$sqrt{s}$$ = 10.520, 10.580, and 10.867 GeV. The search uses data accumulated with the Belle detector at the KEKB asymmetric-energy $$e^+e^-$$ collider. No significant signals are observed in the $$D^{+}D_{s}^{*+}$$ invariant-mass spectra of all studied modes. The 90% credibility level upper limits on their product branching fractions in $$Upsilon(1S)$$ and $$Upsilon(2S)$$ inclusive decays ($${cal B}(Upsilon(1S,2S) to R^{++} + {rm anything}) times {cal B}(R^{++} to D^{+} D_{s}^{*+})$$), and the product values of Born cross section and branching fraction in $$e^+e^-$$ collisions ($$sigma(e^+e^- to R^{++} + {rm anything}) times {cal B}(R^{++} to D^{+} D_{s}^{*+})$$) at $$sqrt{s}$$ = 10.520, 10.580, and 10.867 GeV under different assumptions of $$R^{++}$$ masses varying from 4.13 to 4.17 GeV/$$c^2$$, and widths varying from 0 to 5 MeV are obtained.

論文

Study of electromagnetic decays of orbitally excited $$Xi_c$$ Baryons

Yelton, J.*; 谷田 聖; Belle Collaboration*; 他208名*

Physical Review D, 102(7), p.071103_1 - 071103_8, 2020/10

https://doi.org/10.1103/PhysRevD.102.071103
 被引用回数：8 パーセンタイル：51.82(Astronomy & Astrophysics)

Using 980 fb$$^{-1}$$ of data collected with the Belle detector operating at the KEKB asymmetric-energy $$e^+e^-$$ collider, we report a study of the electromagnetic decays of excited ${charmed baryons}$ $$Xi_c(2790)$$ and $$Xi_c(2815)$$. A clear signal (8.6 standard deviations) is observed for $$Xi_c(2815)^0 to Xi_c^0gamma$$, and we measure: $$B[Xi_c(2815)^0 to Xi_c^0gamma]/B[Xi_c(2815)^0 to Xi_c(2645)^+pi^- to Xi_c^0pi^+pi^-] = 0.41 pm 0.05 pm 0.03$$. We also present evidence (3.8 standard deviations) for the similar decay of the $$Xi_c(2790)^0$$ and measure: $$B[Xi_c(2790)^{0}toXi_c^{0}gamma]/B[Xi_c(2790)^0toXi_c^{prime +}pi^{-}toXi_c^{+}gamma pi^-] = 0.13 pm 0.03 pm 0.02$$. The first quoted uncertainties are statistical and the second systematic. We find no hint of the analogous decays of the $$Xi_c(2815)^+$$ and $$Xi_c(2790)^+$$ baryons and set upper limits at the 90% confidence level of: $$B[Xi_c(2815)^{+}toXi_c^{+}gamma]/B[Xi_c(2815)^+toXi_c(2645)^0pi^+toXi_c^+pi^-pi^+] < 0.09,$$ and $$B[Xi_c(2790)^{+}toXi_c^{+}gamma]/B[Xi_c(2790)^+toXi_c^{prime0}pi^{+}toXi_c^{0}gamma pi^+] < 0.06.$$ Approximate values of the partial widths of the decays are extracted, which can be used to discriminate between models of the underlying quark structure of these excited states.

論文

Measurement of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ with a semileptonic tagging method

Caria, G.*; 谷田 聖; Belle Collaboration*; 他202名*

Physical Review Letters, 124(16), p.161803_1 - 161803_8, 2020/04

https://doi.org/10.1103/PhysRevLett.124.161803
 被引用回数：76 パーセンタイル：97.68(Physics, Multidisciplinary)

The experimental results on the ratios of branching fractions $$mathcal{R}(D) = {cal B}(bar{B} to D tau^- bar{nu_{tau}})/{cal B}(bar{B} to D ell^- barnu_{ell})$$ and $$mathcal{R}(D^*) = {cal B}(bar{B} to D^* tau^- bar{nu_{tau}})/{cal B}(bar{B} to D^* ell^- bar{nu_{ell}})$$, where $$ell$$ denotes an electron or a muon, show a long-standing discrepancy with the Standard Model predictions, and might hint to a violation of lepton flavor universality. We report a new simultaneous measurement of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$, based on a data sample containing $$772 times 10^6$$ $$Bbar{B}$$ events recorded at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. In this analysis the tag-side $$B$$ meson is reconstructed in a semileptonic decay mode and the signal-side $$tau$$ is reconstructed in a purely leptonic decay. The measured values are $$mathcal{R}(D)= 0.307 pm 0.037 pm 0.016$$ and $$mathcal{R}(D^*) = 0.283 pm 0.018 pm 0.014$$, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within $$0.2$$, $$1.1$$ and $$0.8$$ standard deviations for $$mathcal{R}(D)$$, $$mathcal{R}(D^*)$$ and their combination, respectively. This work constitutes the most precise measurements of $$mathcal{R}(D)$$ and $$mathcal{R}(D^*)$$ performed to date as well as the first result for $$mathcal{R}(D)$$ based on a semileptonic tagging method.

論文

Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment

Abudin$'e$n, F.*; 谷田 聖; Belle II Collaboration*; 他420名*

Chinese Physics C, 44(2), p.021001_1 - 021001_12, 2020/02

https://doi.org/10.1088/1674-1137/44/2/021001
 被引用回数：23 パーセンタイル：93.93(Physics, Nuclear)

From April to July 2018, a data sample at the peak energy of the $$Upsilon(4S)$$ resonance was collected with the Belle II detector at the SuperKEKB electron-positron collider. This is the first data sample of the Belle II experiment. Using Bhabha and digamma events, we measure the integrated luminosity of the data sample to be ($$496.3 pm 0.3 pm 3.0$$) pb$$^{-1}$$, where the first uncertainty is statistical and the second is systematic. This work provides a basis for future luminosity measurements at Belle II.

論文

Transverse single spin asymmetry for very forward $$pi^0$$ production in polarized proton-proton collisions at $$sqrt s$$ = 510 GeV

Kim, M. H.*; 谷田 聖; 他20名*

EPJ Web of Conferences, 208, p.05007_1 - 05007_4, 2019/05

https://doi.org/10.1051/epjconf/201920805007
 被引用回数：0 パーセンタイル：0.06(Astronomy & Astrophysics)

Transverse single spin asymmetry, $$A_{N}$$, of very forward $$pi^{0}$$ production from polarized $$p + p$$ collisions provides new information toward an understanding of its production mechanism. $$A_{N}$$ of forward $$pi^{0}$$ in the pseudorapidity region of $$3 < eta < 4$$ has been described by the partonic structure of the proton in the perturbative QCD framework. However, recent data indicates a potential contribution from not only partonic but also diffractive interactions. In order to provide a new insight on the origin of the $$A_{N}$$, we measured the very forward $$pi^{0}$$ production in the pseudorapidity region of $$6 < eta$$ from $$sqrt{s}$$ = 510 GeV polarized $$p + p$$ collisions at RHIC in 2017. We report our measurement of the very forward $$pi^{0}$$ over the transverse momentum range of $$0 < p_{T} < 1$$ GeV/$$c$$ and the preliminary result.

論文

Observation of $$B^{+} rightarrow pbar{Lambda} K^+ K^-$$ and $$B^{+} rightarrow bar{p}Lambda K^+ K^+$$

Lu, P.-C.*; 谷田 聖; Belle Collaboration*; 他203名*

Physical Review D, 99(3), p.032003_1 - 032003_9, 2019/02

AA2019-0533.pdf:1.04MB

https://doi.org/10.1103/PhysRevD.99.032003
 被引用回数：5 パーセンタイル：31.16(Astronomy & Astrophysics)

We report the study of $$B^{+} rightarrow pbar{Lambda} K^+ K^-$$ and $$B^{+} rightarrow bar{p}Lambda K^+ K^+$$ using a $$772 times 10^6$$ $$Bbar{B}$$ pair data sample recorded on the $$Upsilon({rm 4S})$$ resonance with the Belle detector at KEKB. These include the observations of decay modes with the corresponding branching fractions $$mathcal{B}$$($$B^{+} rightarrow pbar{Lambda} K^+ K^-$$) $$=$$ $$(4.22^{+0.45}_{-0.44}pm 0.51) times10^{-6}$$, $$mathcal{B}$$($$B^{+} rightarrow bar{p}Lambda K^+ K^+$$) $$=$$ $$(3.81^{+0.39}_{-0.37} pm 0.45)times 10^{-6}$$, $$mathcal{B}$$($$eta_c rightarrow p bar{Lambda} K^-$$) $$=$$ $$(2.9^{+0.4}_{-0.3}pm 0.4)times10^{-3}$$ and $$mathcal{B}$$($$B^{+} rightarrow pbar{Lambda} phi$$) $$=$$ $$(0.818 pm 0.215 pm 0.078)times10^{-6}$$, where $$mathcal{B}$$ denotes the decay branching fraction and the intermediate resonance decays are excluded in the four-body decay measurements.

論文

Observation of transverse $$Lambda/bar{Lambda}$$ hyperon polarization in $$e^+e^-$$ annihilation at Belle

Guan, Y.*; 谷田 聖; Belle Collaboration*; 他205名*

Physical Review Letters, 122(4), p.042001_1 - 042001_8, 2019/02

AA2019-0532.pdf:0.4MB

https://doi.org/10.1103/PhysRevLett.122.042001
 被引用回数：28 パーセンタイル：85.72(Physics, Multidisciplinary)

We report the first observation of the spontaneous polarization of $$Lambda$$ and $$bar{Lambda}$$ hyperons transverse to the production plane in $$e^+e^-$$ annihilation, which is attributed to the effect arising from a polarizing fragmentation function. For inclusive $$Lambda/bar{Lambda}$$ production, we also report results with subtracted feed-down contributions from $$Sigma^0$$ and charm. This measurement uses a dataset of 800.4 fb$$^{-1}$$ collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV. We observe a significant polarization that rises with the fractional energy carried by the $$Lambda/bar{Lambda}$$ hyperon.

論文

Measurement of very forward particle production at RHIC with $$sqrt s=$$ 510 GeV proton-proton collisions

さこ 隆志*; 谷田 聖; 他20名*

Proceedings of Science (Internet), 301, p.337_1 - 337_8, 2018/08

https://doi.org/10.22323/1.301.0337

The Relativistic Heavy Ion Collider forward (RHICf) experiment has measured neutral particles produced in the very forward direction in the $$sqrt s=$$ 510 GeV proton-proton collisions at RHIC in June 2017. The production cross sections of these particles are crucial to understand the hadronic interaction relevant to the air shower development at the cosmic-ray equivalent energy of $$1.4times 10^{14}$$ eV, just below the energy of the knee. Together with the data at LHC, accelerator data can cover the interaction in the cosmic-ray energy of 10$$^{14}$$ eV to 10$$^{17}$$ eV. In addition, RHICf is able to improve the former measurements of single-spin asymmetry in the polarized proton-proton collisions that is sensitive to the fundamental process of the meson exchange. Common data taking with the STAR experiment will shed light on the unexplored low mass diffraction process.

論文

Systematic study of azimuthal anisotropy in Cu + Cu and Au + Au collisions at $$sqrt{s_{NN}}$$ = 62.4 and 200 GeV

Adare, A.*; 今井 憲一; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他420名*

Physical Review C, 92(3), p.034913_1 - 034913_20, 2015/09

AA2015-0713.pdf:1.3MB

https://doi.org/10.1103/PhysRevC.92.034913
 被引用回数：20 パーセンタイル：78.02(Physics, Nuclear)

We have studied the dependence of azimuthal anisotropy $$v_2$$ for inclusive and identified charged hadrons in Au + Au and Cu + Cu collisions on collision energy, species, and centrality. The values of $$v_2$$ as a function of transverse momentum $$p_T$$ and centrality in Au+Au collisions at $$sqrt{s_{NN}}$$ = 200 and 62.4 GeV are the same within uncertainties. However, in Cu + Cu collisions we observe a decrease in $$v_2$$ values as the collision energy is reduced from 200 to 62.4 GeV. The decrease is larger in the more peripheral collisions. By examining both Au + Au and Cu + Cu collisions we find that $$v_2$$ depends both on eccentricity and the number of participants, $$N_{rm part}$$. We observe that $$v_2$$ divided by eccentricity ($$epsilon$$) monotonically increases with $$N_{rm part}$$ and scales as $$N_{rm part}^{1/3}$$. The Cu + Cu data at 62.4 GeV falls below the other scaled $$v_2$$ data. For identified hadrons, $$v_2$$ divided by the number of constituent quarks $$n_q$$ is independent of hadron species as a function of transverse kinetic energy $$KE_T=m_T-m$$ between $$0.1 < KE_T/n_q < 1$$ GeV. Combining all of the above scaling and normalizations, we observe a near-universal scaling, with the exception of the Cu + Cu data at 62.4 GeV, of $$v_2/(n_q cdot epsilon cdot N_{rm part}^{1/3})$$ vs $$KE_T/n_q$$ for all measured particles.

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