arXiv subjects

Seiji Matsumoto

Publications and source records attributed to Seiji Matsumoto.

9 recordsLinked to original sources

arXiv2026

Glauber-Lachs formula-based analysis of three-pion Bose-Einstein correlation data in $pp$ collisions at 7 TeV from the LHCb Collaboration

In this study, we combine the Glauber--Lachs formula from quantum optics and the two-component picture for pion production to analyze data on two- and three-pion Bose--Einstein correlation in $pp$ collisions at 7 TeV from the LHCb Collaboration. For the pion exchange function $E_{\rm 2B}$, we chose a dipole form and an inverse one-and-a-half pole form. The extensions are computed in the configuration space of four-dimensional Euclidean space ($ξ=\sqrt{|r_1-r_2|^2+(t_1-t_2)^2}$).

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arXiv2024

Analysis of the L3 BEC at Z$^0$-pole -- Comparison of the conventional formula against the $τ$-model

The L3 Collaboration reported data on 2-jet and 3-jet Bose--Einstein correlations (BECs) with the results obtained through the $τ$-model in 2011. In this study, we analyze these correlations using the conventional formula with the Gaussian long-range correlation (${\rm CF_I\times LRC_{(Gauss)}}$). The estimated ranges of interactions for 2-jet and 3-jet, $R_{\rm 2-jet}$ and $R_{\rm 3-jet}$, are almost the same magnitude as those by $τ$-model: $R_{\rm 2-jet}=0.83\pm 0.05$ (stat) fm and $R_{\rm 3-jet}=1.09\pm 0.04$ (stat) fm. The anticorrelation in BEC (less than 1.0) observed by the L3 Collaboration is related to the partially negative density profile ($ρ_{\rm τ, BE}(ξ)$ in $ξ$ space) in the $τ$-model and the ${\rm LRC_{(Gauss)}}=1/(1+αe^{-βQ^2})$ in ${\rm CF_I\times LRC_{(Gauss)}}$, respectively. Remarkably, the probability $P_τ(ξ)$ calculated from the Levy canonical form exhibits partially negative behavior.

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arXiv2023

Two-component model description of Bose-Einstein correlations in pp collisions at 13 TeV measured by the CMS Collaboration at the LHC

Using the two-component model, we analyze Bose-Einstein correlations in pp collisions at the center-of-mass energy of 13 TeV, measured by the CMS Collaboration at the LHC, and compare results with the $τ$-model. We utilize data described by the double ratios with an average pair transverse momentum $0\le k_T\le 1.0$ GeV and six intervals described by the reconstructed charged particle multiplicity as $N_{\rm trk}^{\rm offline}$. The estimated ranges are 1-4 fm for the magnitude of extension of emitting source expressed by the exponential function $\exp(-RQ)$ and 0.4-0.5 fm for that by the Gaussian distribution $\exp(-(RQ)^2))$, respectively. Moreover, we estimate the upper limits of the 3-pion BEC to test the two-component model and investigate the role of the long-range correlation.

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arXiv2022

Analysis of OPAL Bose-Einstein Correlation at $Z^0$-pole by the second conventional formula

We can obtain a second conventional formula (${\rm CF_{II}}$) with two components by extending the conventional formula ${\rm CF_{I}}$ with one component for Bose-Einstein Correlation (BEC). We used ${\rm CF_{II}}$ to analyze the BEC at $Z^0$-pole as part of the OPAL collaboration. $R_1({\rm G})=0.91\pm 0.03$ fm ($λ_1=0.61\pm 0.03$) and $R_2({\rm G})=2.57\pm 0.44$ fm ($λ_1=0.35\pm 0.09$) are the estimated interaction region, where $λ_1$ and $λ_2$ are the degrees of coherence, and G is the Gaussian distribution, respectively. Long range correlation (LRC) is also studied.

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arXiv1998

Constraints on Non-Standard Contributions to the Charged-Current Interactions

The success of the quantum level predictions of the Standard Model on the $Z$ boson properties, on $\mw$ and on $\mt$, which makes use of the muon lifetime as an input, implies a stringent constraint on new physics contributions to the $V-A$ charged-current interactions among leptons. Observed unitarity of the CKM matrix elements then implies constraints on non-standard contributions to the lepton-quark charged-current interactions. By using the recent electroweak data as inputs, we find the 95%~CL limits for the corresponding contact interactions: $Λ_{CC,+}^{\ell\ell}>7.5$ TeV and $Λ_{CC,-}^{\ell\ell}>10.2$ TeV for the purely leptonic terms, and $Λ_{CC,+}^{\ell q}>5.8$ TeV and $Λ_{CC,-}^{\ell q}>10.1$~TeV for the lepton-quark contact interactions.

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arXiv1997

Constraints on four-Fermi contact interactions from low-energy electroweak experiments

We investigate the constraints on four-Fermi contact interactions from low-energy lepton-quark and lepton-lepton scattering experiments --- polarization asymmetries in electron (muon)-nucleon scattering experiments, cesium and thallium atom parity violation measurements, neutrino-nuclei and neutrino-electron scattering experiments. These constraints are then combined by assuming the lepton and quark universalities and SU(2)*U(1) gauge invariance of the contact interaction, which leave independent six lepton-quark and three pure-leptonic interactions.Impacts of these constraints on models with an additional Z-boson are briefly discussed. We also present updates of the low-energy constraints on the S and T parameters.

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arXiv1997

Analysis of Electroweak Precision Data and Prospects for Future Improvements

We update our previous work on an analysis of the electroweak data by including new and partly preliminary data available up to the 1996 summer conferences. The new results on the Z partial decay widths into b and c hadrons now offer a consistent interpretation of all data in the minimal standard model. The value extracted for the strong interaction coupling constant α_s(mZ) agrees well with determinations in other areas. New constraints on the universal parameters S, T and U are obtained from the updated measurements. No signal of new physics is found in the S,T,U analysis once the SM contributions with mt \sim 175GeV and those of not a too heavy Higgs boson are accounted for. The naive QCD-like technicolor model is now ruled out at the 99%CL even for the minimal model with SU(2)_{TC}. In the absence of a significant new physics effect in the electroweak observables, constraints on masses of the top quark, mt, and Higgs boson, mH, are derived as a function of α_s and the QED effective coupling $\barα(m_Z^2)$. The preferred range of mH depends rather strongly on the actual value of mt: mH<360 GeV for mt=170GeV, while mH>130GeV for mt=180GeV at 95%CL. Prospects due to forthcoming improved measurements of asymmetries, the mass of the weak boson W mW, mt and $\barα(m_Z^2)$ are discussed. Anticipating uncertainties of 0.00020 for $\sbar^2(m_Z^2)$, 20MeV for mW, and 2GeV for mt, the new physics contributions to the S,T,U parameters will be constrained more severely, and, within the SM, the logarithm of the Higgs mass can be constrained to about +-0.35. The better constraints on S,T,U and on mH within the minimal SM should be accompanied with matching precision in $\barα(m_Z^2)$.

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arXiv1995

Electroweak Precision Measurements and the Minimal Supersymmetric Standard Model

We discuss supersymmetric contributions to the electroweak precision measurements in the Minimal Supersymmetric Standard Model for two cases: the quark-lepton universality violation $δ_{q\ell}$ in charged currents and the ratio $R_b=Γ(Z\rightarrow b\bar{b})/Γ(Z\rightarrow \rm hadrons)$. The recent experimental data suggest deviations from the Standard Model for these observables, at the 1-$σ$ level for the former and at more than 3-$σ$ level for the latter. We analyze the non-oblique corrections from the SUSY particles to explain these discrepancies. The observed non-zero $δ_{q\ell}$ may be explained by relatively light sleptons, charginos and neutralinos. Although the observed excess of $R_b$ can be explained by very light scalar top and chargino for low $\tanβ$, this interpretation is severely constrained by the opening of exotic decay modes for the top quark.

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arXiv1994

Constraints on the electroweak universal parameters and the top and Higgs masses from updated LEP/SLC data

A global analysis is performed using the latest data from LEP and SLC. Constraints on the electroweak universal parameters ($S,T,U$) and on the masses of the top quark and Higgs boson within the Standard Model (SM) are investigated. The uncertainties due to the QCD and QED effective couplings, $α_s(\mz)$ and $\barα(\mmz)$, are examined in detail. Even though the mean value of $S$ is increased to be consistent with zero, the naive Technicolor models are still disfavored due to its reduced error. Within the SM, we find the 90\,\%CL constraints; $133\gev<m_t<190\gev$ and $10\gev<\mh<440\gev$ for $α_s(\mz)=0.116$ and $1/\barα(\mmz) =128.72$. The experimental constraints on the $\zbb$ vertex form-factor, $\delb(\mmz)$, play an important role in disfavoring the region of large $m_t(m_t \sim 200\gev)$ and large $\mh(\mh \sim 1000\gev)$. If $m_t$ is precisely known, the present electroweak data give a rather strict upper bound on the Higgs mass, $\mh<140\,(300)\gev\,$ at 95\%~CL, for $m_t=160\, (175)\gev$ and for the above $α_s(\mz)$ and $\barα(\mmz)$.

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