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論文

Observation of Coulomb-assisted nuclear bound state of $$Xi^-$$-$$^{14}$$N system

早川 修平; 藤田 真奈美; 長谷川 勝一; 橋本 直; 細見 健二; 市川 裕大; 今井 憲一*; 七村 拓野; 成木 恵; 佐甲 博之; et al.

Physical Review Letters, 126(6), p.062501_1 - 062501_6, 2021/02

 被引用回数:6 パーセンタイル:96.42(Physics, Multidisciplinary)

In an emulsion-counter hybrid experiment performed at J-PARC, a $$Xi^-$$ absorption event was observed which decayed into twin single-$$Lambda$$ hypernuclei. Kinematic calculations enabled a unique identification of the reaction process as $$Xi^{-} + ^{14}$$N$$ rightarrow ^{10}_Lambda$$Be + $$^5_Lambda$$He. For the binding energy of the $$Xi^{-}$$ hyperon in the $$Xi^-$$-$$^{14}$$N system a value of $$1.27 pm 0.21$$ MeV was deduced. The energy level of $$Xi^-$$ is likely a nuclear $$1p$$ state which indicates a weak $${Xi}N$$-$$LambdaLambda$$ coupling.

論文

Production of $$bbar{b}$$ at forward rapidity in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV

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 ($$bbar{b}$$) production in $$p+p$$ collisions at $$sqrt{s}=510$$ 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 ($$1.2 < |y| < 2.2$$). The $$bbar{b}$$ signal is extracted from like-sign dimuons by utilizing the unique properties of neutral $$B$$ meson oscillation. We report a differential cross section of $$dsigma_{bbar{b} rightarrow mu^pmmu^pm}/dy = 0.16 pm 0.01~(mbox{stat}) pm 0.02~(mbox{syst}) pm 0.02~(mbox{global})$$ nb for like-sign muons in the rapidity and $$p_T$$ ranges $$1.2 < |y| < 2.2$$ and $$p_T > 1$$ GeV/$$c$$, and dimuon mass of 5 - 10 GeV/$$c^2$$. The extrapolated total cross section at this energy for $$bbar{b}$$ production is $$13.1 pm 0.6~(mbox{stat}) pm 1.5~(mbox{syst}) pm 2.7~(mbox{global})~mu$$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 $$bbar{b}$$ decays and their $$p_T$$ distributions are compared to distributions generated using ${sc ps pythia 6}$, which includes next-to-leading order processes. The azimuthal correlations and pair $$p_T$$ distribution are not very well described by ${sc pythia}$ calculations, but are still consistent within uncertainties. Flavor creation and flavor excitation subprocesses are favored over gluon splitting.

論文

Search for transitions from $$Upsilon(4S)$$ and $$Upsilon(5S)$$ to $$eta_b(1S)$$ and $$eta_b(2S)$$ with emission of an $$omega$$ meson

Oskin, P.*; 谷田 聖; Belle Collaboration*; 他198名*

Physical Review D, 102(9), p.092011_1 - 092011_8, 2020/11

 被引用回数:0 パーセンタイル:0.01(Astronomy & Astrophysics)

Using data collected in the Belle experiment at the KEKB asymmetric-energy $$e^+e^-$$ collider we search for transitions $$Upsilon(4S) rightarrow eta_b(1S)omega$$, $$Upsilon(5S) rightarrow eta_b(1S)omega$$ and $$Upsilon(5S) rightarrow eta_b(2S)omega$$. No significant signals are observed and we set 90% confidence level upper limits on the corresponding visible cross sections: $$0.2 ~textrm{pb}, 0.4 ~textrm{pb}$$ and $$1.9 ~textrm{pb}$$, respectively.

論文

Observation of a $$bar{K}NN$$ bound state in the $$^3{rm He} (K^-, Lambda p)n$$ reaction

山我 拓巳*; 橋本 直; 谷田 聖; 他66名*

Physical Review C, 102(4), p.044002_1 - 044002_14, 2020/10

 被引用回数:2 パーセンタイル:38.19(Physics, Nuclear)

We have performed an exclusive measurement of the $$K^{-}+! ~^{3}{rm He} to Lambda pn$$ reaction at an incident kaon momentum of $$1 {rm GeV}/c$$. In the $$Lambda p$$ invariant mass spectrum, a clear peak was observed below the mass threshold of $$bar{K}+N+N$$, as a signal of the kaonic nuclear bound state, $$bar{K}NN$$. The binding energy, decay width, and $$S$$-wave Gaussian reaction form-factor of this state were observed to be $$B_{K} = 42pm3({rm stat.})^{+3}_{-4}({rm syst.}) {rm MeV}$$, $$Gamma_{K} = 100pm7({rm stat.})^{+19}_{-9}({rm syst.}) {rm MeV}$$, and $$Q_{K} = 383pm11({rm stat.})^{+4}_{-1}({rm syst.}) {rm MeV}/c$$, respectively. The total production cross-section of $$bar{K}NN$$, determined by its $$Lambda p$$ decay mode, was $$sigma^{tot}_{K} cdot BR_{Lambda p} = 9.3pm0.8({rm stat.})^{+1.4}_{-1.0}({rm syst.}) mu{rm b}$$. We estimated the branching ratio of the $$bar{K}NN$$ state to the $$Lambda p$$ and $$Sigma^{0}p$$ decay modes as $$BR_{Lambda p}/BR_{Sigma ^{0}p} sim 1.7$$, by assuming that the physical processes leading to the $$Sigma N!N$$ final states are analogous to those of $$Lambda pn$$.

論文

Polarization and cross section of midrapidity $$J/psi$$ production in $$p+p$$ collisions at $$sqrt{s}=510$$ GeV

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:0 パーセンタイル:0.01(Astronomy & Astrophysics)

The PHENIX experiment has measured the spin alignment for inclusive $$J/psi rightarrow e^{+}e^{-}$$ decays in $$p+p$$ collisions at $$sqrt{s}=510$$ 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 $$0.0 < p_T < 10.0$$ GeV/$$c$$. The results are consistent with a previous one-dimensional analysis at midrapidity at $$sqrt{s}=200$$ GeV. The transverse-momentum-dependent cross section for midrapidity $$J/psi$$ production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on $$sqrt{s}$$.

論文

Measurement of the charm-mixing parameter $$y_{CP}$$ in $$D^{0}to K^{0}_{S}omega$$ decays at Belle

Nayak, M.*; 谷田 聖; Belle Collaboration*; 他180名*

Physical Review D, 102(7), p.071102_1 - 071102_8, 2020/10

 被引用回数:1 パーセンタイル:24.96(Astronomy & Astrophysics)

We report the first measurement of the charm-mixing parameter $$y_{CP}$$ in $$D^{0}$$ decays to the $$CP$$-odd final state $$K^{0}_{S}omega$$. The study uses the full Belle $$e^{+}e^-$$ annihilation data sample of $$976rm~ fb^{-1}$$ taken at or near the $$Upsilon(4S)$$ centre-of-mass energy. We find $$y_{CP} = (0.96 pm 0.91 pm 0.61 {}^{+0.17}_{-0.00})%$$, where the first uncertainty is statistical, the second is systematic due to event selection and background, and the last is due to possible presence of $$CP$$-even decays in the data sample.

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

 被引用回数:1 パーセンタイル:24.96(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

Search for axionlike particles produced in $$e^+e^-$$ collisions at Belle II

Abudin$'e$n, F.*; 谷田 聖; Belle II Collaboration*; 他334名*

Physical Review Letters, 125(16), p.161806_1 - 161806_9, 2020/10

 被引用回数:4 パーセンタイル:74.08(Physics, Multidisciplinary)

We present a search for the direct production of a light pseudoscalar $$a$$ decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process $${e^+e^-togamma a, a togammagamma}$$ in the mass range $${0.2} , < m_a < {9.7},$$${GeV/$c^2$}$ using data corresponding to an integrated luminosity of $$(445pm 3),$$pb$$^{-1}$$. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axion-like particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength $$g_{agammagamma}$$ of ALPs to photons at the level of $$10^{-3},$$GeV$$^{-1}$$. The limits are the most restrictive to date for $$0.2, < ,m_a, < ,1,$$GeV/$$c^2$$.

論文

Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=510$$ GeV

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:1 パーセンタイル:24.96(Astronomy & Astrophysics)

The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, $$A_{LL}$$, for charged pions at midrapidity ($$|eta| < 0.35$$) in longitudinally polarized $$p$$$$+$$$$p$$ collisions at $$sqrt{s}=510$$ GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction $$x$$ 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 $$sqrt{s}=200$$ GeV, which show a nonzero positive contribution of gluon spin to the proton spin.

論文

Measurement of $$J/psi$$ at forward and backward rapidity in $$p$$+$$p$$, $$p$$$$+A$$l, $$p$$$$+A$$u, and $$^3$$He+Au collisions at $$sqrt{s_{_{NN}}}$$ = 200 GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他358名*

Physical Review C, 102(1), p.014902_1 - 014902_23, 2020/07

 被引用回数:1 パーセンタイル:38.19(Physics, Nuclear)

Charmonium is a valuable probe in heavy-ion collisions to study the properties of the quark gluon plasma, and is also an interesting probe in small collision systems to study cold nuclear matter effects, which are also present in large collision systems. With the recent observations of collective behavior of produced particles in small system collisions, measurements of the modification of harmonium in small systems have become increasingly relevant. We present the results of $$J/psi$$ measurements at forward and backward rapidity in various small collision systems, $$p$$$$+$$$$p$$, $$p$$$$+$$Al, $$p$$$$+$$Au and $$^3$$He$$+$$Au, at $$sqrt{s_{_{NN}}}$$=200 GeV. The results are presented in the form of the observable $$R_{AB}$$, the nuclear modification factor, a measure of the ratio of the $$J/psi$$ invariant yield compared to the scaled yield in $$p$$$$+$$$$p$$ collisions. We examine the rapidity, transverse momentum, and collision centrality dependence of nuclear effects on $$J/psi$$ production with different projectile sizes $$p$$ and $$^3$$He, and different target sizes Al and Au. The modification is found to be strongly dependent on the target size, but to be very similar for $$p$$$$+$$Au and $$^{3}$$He$$+$$Au. However, for 0% - 20% central collisions at backward rapidity, the modification for $$^{3}$$He$$+$$Au is found to be smaller than that for $$p$$$$+$$Au, with a mean fit to the ratio of $$0.89pm0.03$$(stat)$${pm}0.08$$(syst), possibly indicating final state effects due to the larger projectile size.

論文

Search for $$B^0$$ decays to invisible final states ($$+gamma$$) at Belle

Ku, Y.*; 谷田 聖; Belle Collaboration*; 他153名*

Physical Review D, 102(1), p.012003_1 - 012003_9, 2020/07

 被引用回数:1 パーセンタイル:24.96(Astronomy & Astrophysics)

We report searches for $$B^0torm{invisible}$$ and $$B^0torm{invisible}+gamma$$ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a $$711,{rm fb}^{-1}$$ data sample that contains $$772 times 10^6 Bbar{B}$$ pairs and was collected near the $$Upsilon,(4S)$$ resonance with the Belle detector at the KEKB $$e^+ e^-$$ collider. We observe no significant signal for either decay and set upper limits on their branching fractions at $$90%$$ confidence level of $$mathcal{B},(B^0torm{invisible}) < 7.8times10^{-5}$$ and $$mathcal{B},(B^0torm{invisible}+gamma) < 1.6times10^{-5}$$.

論文

Dalitz analysis of $$D^{0}to K^{-}pi^{+}eta$$ decays at Belle

Chen, Y. Q.*; 谷田 聖; Belle Collaboration*; 他181名*

Physical Review D, 102(1), p.012002_1 - 012002_12, 2020/07

 被引用回数:3 パーセンタイル:56.47(Astronomy & Astrophysics)

We present the results of the first Dalitz plot analysis of the decay $$D^{0}to K^{-}pi^{+}eta$$. The analysis is performed on a data set corresponding to an integrated luminosity of 953 $$rm{fb}^{-1}$$ collected by the Belle detector at the asymmetric-energy $$e^{+}e^{-}$$ KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels $$bar{K}^{*}(892)^0eta$$, $$K^{-}a_0(980)^+$$, $$K^{-}a_2(1320)^+$$, $$bar{K}^{*}(1410)^0eta$$, $$K^{*}(1680)^-pi^{+}$$ and $$K_2^{*}(1980)^-pi^{+}$$, together with $$Kpi$$ and $$Keta$$ S-wave components. The decays $$K^{*}(1680)^{-}to K^{-}eta$$ and $$K_{2}^{*}(1980)^{-}to K^{-}eta$$ are observed for the first time. We measure ratio of the branching fractions, $$frac{mathcal{B}(D^{0}to K^{-}pi^{+}eta)}{mathcal{B}(D^{0}to K^{-}pi^{+})}$$ =0.500 $$pm 0.002 {rm(stat)} pm0.020 {rm(syst)}pm 0.003 {rm (mathcal{B}_{PDG})}$$. Using the Dalitz fit result, the ratio $$frac{mathcal{B}(K^{*}(1680) to K eta)}{mathcal{B}(K^{*}(1680)to Kpi)}$$ is measured to be $$0.11 pm 0.02 {rm(stat)}^{+0.06}_{-0.04}{rm(syst)} pm 0.04{rm(mathcal{B}_{{PDG}})}$$; this is much lower than the theoretical expectations ($$approx 1$$) made under the assumption that $$K^{*}(1680)$$ is a pure $$1^{3}D_1$$ state. The product branching fraction $$mathcal{B}(D^0 to [K_2^{*}(1980)^- to K^{-} eta] pi^{+}) = (2.2^{+1.7}_{-1.9})times10^{-4}$$ is determined. In addition, the $$pieta^{prime}$$ contribution to the $$a_0(980)^{pm}$$ resonance shape is confirmed with 10.1$$sigma$$ statistical significance using the three-channel Flatte model. We also measure $$mathcal{B}(D^0tobar{K}^{*}(892)^0eta)=(1.41^{+0.13}_{-0.12})%$$. This is consistent with, and more precise than, the current world average $$(1.02pm0.30)%$$, deviates with a significance of more than $$3sigma$$ from the theoretical predictions of (0.51-0.92)%.

論文

Roper-like resonances with various flavor contents and their two-pion emission decays

Arifi, A. J.*; 永廣 秀子*; 保坂 淳; 谷田 聖

Physical Review D, 101(11), p.111502_1 - 111502_5, 2020/06

 被引用回数:8 パーセンタイル:81.48(Astronomy & Astrophysics)

We study the three-body decay of the newly observed bottom baryon $$Lambda_b^*(6072)$$ by LHCb; $$Lambda_b^*(6072) to Lambda_b pi pi$$. Its mass about 500 MeV above the ground state $$Lambda_b$$ and a broad width imply that the state could be an analogue of the Roper resonance of the nucleon $$N(1440)$$. In terms of sequential processes going through $$Sigma_b$$ and $$Sigma_b^*$$, we find that the observed invariant mass distribution is reproduced assuming its spin and parity $$J^P = 1/2^+$$. We discuss that the ratio of the two sequential processes and angular correlation of two pions are useful for the determination of spin and parity. We suggest further studies for the Roper resonance analogue in various flavor contents, raising an interesting and important question in baryon spectroscopy.

論文

Transverse single-spin asymmetry for very forward neutral pion production in polarized $$p+p$$ collisions at $$sqrt{s}$$ = 510 GeV

Kim, M. H.*; 谷田 聖; RHICf Collaboration*; 他23名*

Physical Review Letters, 124(25), p.252501_1 - 252501_6, 2020/06

 被引用回数:2 パーセンタイル:54.33(Physics, Multidisciplinary)

Transverse single-spin asymmetries of very forward neutral pions generated in polarized $$p + p$$ collisions allow us to understand the production mechanism in terms of perturbative and non-perturbative strong interactions. During 2017 the RHICf Collaboration installed an electromagnetic calorimeter in the zero-degree region of the STAR detector at the Relativistic Heavy Ion Collider (RHIC) and measured neutral pions produced at pseudorapidity larger than 6 in polarized $$p$$+$$p$$ collisions at $$sqrt{s}$$ = 510 GeV. The large non-zero asymmetries increasing both in longitudinal momentum fraction $$x_{F}$$ and transverse momentum $$p_{T}$$ have been observed at low transverse momentum $$p_{T} < 1$$ GeV/$$c$$ for the first time at this collision energy. The asymmetries show an approximate $$x_{F}$$ scaling in the $$p_{T}$$ region where non-perturbative processes are expected to dominate. A non-negligible contribution from soft processes may be necessary to explain the nonzero neutral pion asymmetries.

論文

First search for the $$eta_{c2}(1D)$$ in $$B$$ decays at Belle

Chilikin, K.*; 谷田 聖; Belle Collaboration*; 他194名*

Journal of High Energy Physics (Internet), 2020(5), p.34_1 - 34_22, 2020/05

 被引用回数:2 パーセンタイル:43.33(Physics, Particles & Fields)

The first dedicated search for the $$eta_{c2}(1D)$$ is carried out using the decays $$B^+ rightarrow eta_{c2}(1D) K^+$$, $$B^0 rightarrow eta_{c2}(1D) K^0_S$$, $$B^0 rightarrow eta_{c2}(1D) pi^- K^+$$, and $$B^+ rightarrow eta_{c2}(1D) pi^+ K^0_S$$ with $$eta_{c2}(1D) to h_c gamma$$. No significant signal is found. For the $$eta_{c2}(1D)$$ mass range between $$3795$$ and $$3845 mathrm{MeV}/c^2$$, the branching-fraction upper limits are determined to be $$mathcal{B}(B^+ rightarrow eta_{c2}(1D) K^+) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 3.7 times 10^{-5}$$, $$mathcal{B}(B^0 rightarrow eta_{c2}(1D) K^0_S) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 3.5 times 10^{-5}$$, $$mathcal{B}(B^0 rightarrow eta_{c2}(1D) pi^- K^+) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 1.0 times 10^{-4}$$, and $$mathcal{B}(B^+ rightarrow eta_{c2}(1D) pi^+ K^0_S) times mathcal{B}(eta_{c2}(1D) to h_c gamma) < 1.1 times 10^{-4}$$ at 90% C. L. The analysis is based on the 711 $$mathrm{fb}^{-1}$$ data sample collected on the $$Upsilon(4S)$$ resonance by the Belle detector, which operated at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Update of inclusive cross sections of single and pairs of identified light charged hadrons

Seidl, R.*; 谷田 聖; Belle Collaboration*; 他136名*

Physical Review D, 101(9), p.092004_1 - 092004_13, 2020/05

 被引用回数:1 パーセンタイル:24.96(Astronomy & Astrophysics)

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a 558 fb$$^{-1}$$ data sample collected at the $$Upsilon(4S)$$ resonance with the Belle detector at the KEKB asymmetric-energy $$e^+ e^-$$ collider.

論文

Evidence for a vector charmoniumlike state in $$e^+e^- to D^+_sD^*_{s2}(2573)^-+c.c.$$

Jia, S.*; 谷田 聖; Belle Collaboration*; 他175名*

Physical Review D, 101(9), p.091101_1 - 091101_8, 2020/05

 被引用回数:5 パーセンタイル:65.46(Astronomy & Astrophysics)

We report the measurement of $$e^+e^- to D^+_sD^*_{s2}(2573)^-+c.c.$$ via initial-state radiation using a data sample of an integrated luminosity of 921.9 fb$$^{-1}$$ collected with the Belle detector at the $$Upsilon(4S)$$ and nearby. We find evidence for an enhancement with a 3.4$$sigma$$ significance in the invariant mass of $$D^+_sD^*_{s2}(2573)^- +c.c.$$ The measured mass and width are $$(4619.8^{+8.9}_{-8.0}({rm stat.})pm2.3({rm syst.}))~{rm MeV}/c^{2}$$ and $$(47.0^{+31.3}_{-14.8}({rm stat.})pm4.6({rm syst.}))~{rm MeV}$$, respectively. The mass, width, and quantum numbers of this enhancement are consistent with the charmonium-like state at 4626 MeV/$$c^2$$ recently reported by Belle in $$e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$$ The product of the $$e^+e^-to D^+_sD^*_{s2}(2573)^-+c.c.$$ cross section and the branching fraction of $$D^*_{s2}(2573)^-to{bar D}^0K^-$$ is measured from $$D^+_sD^*_{s2}(2573)^-$$ threshold to 5.6 GeV.

論文

Three-body decay of $$Lambda_c^{*} (2765)$$ and determination of its spin-parity

Arifi, A. J.*; 永廣 秀子*; 保坂 淳; 谷田 聖

Physical Review D, 101(9), p.094023_1 - 094023_17, 2020/05

 被引用回数:6 パーセンタイル:71.98(Astronomy & Astrophysics)

We study three-body decays of $$Lambda_c^{*}(2765) to Lambda_c^+pi^+pi^-$$ by using effective Lagrangians in a non-relativistic framework. We consider the sequential decays through $$Sigma_c(2455)pi$$ and $$Sigma_c^*(2520)pi$$ in intermediate states which are dominant contributions. The coupling constants in the effective Lagrangians are computed in the quark model. We demonstrate that the ratio $$R= Gamma(Lambda_c^*toSigma_c^*(2520)pi)/Gamma(Lambda_c^*to Sigma_c(2455)pi)$$ and angular correlations are sensitive to the spin and parity of $$Lambda_c^{*}(2765)$$. Thus, the measurement of these observables in experimental facilities such as Belle and LHCb can provide useful constraints to determine the spin and parity of $$Lambda_c^{*}(2765)$$.

論文

Search for an invisibly decaying $$Z^{prime}$$ boson at Belle II in $$e^+ e^- to mu^+ mu^- (e^{pm} mu^{mp})$$ plus missing energy final states

足立 一郎*; 谷田 聖; Belle II Collaboration*; 他358名*

Physical Review Letters, 124(14), p.141801_1 - 141801_9, 2020/04

 被引用回数:11 パーセンタイル:92.67(Physics, Multidisciplinary)

Theories beyond the standard model often predict the existence of an additional neutral boson, the $$Z^{prime}$$. Using data collected by the Belle II experiment during 2018 at the SuperKEKB collider, we perform the first searches for the invisible decay of a $$Z^{prime}$$ in the process $$e^+ e^- to mu^+ mu^- Z^{prime}$$ and of a lepton-flavor-violating $$Z^{prime}$$ in $$e^+ e^- to e^{pm} mu^{mp} Z^{prime}$$. We do not find any excess of events and set 90% credibility level upper limits on the cross sections of these processes. We translate the former, in the framework of an $$L_{mu}-L_{tau}$$ theory, into upper limits on the $$Z^{prime}$$ coupling constant at the level of $$5 times 10^{-2}$$ - $$1$$ for $$M_{Z^prime}leq 6$$ GeV/$$c^2$$.

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

 被引用回数:17 パーセンタイル:96.37(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.

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