Search results for "Quark"

Semileptonic and nonleptonic decays of B c

2007

Using our relativistic constituent quark model we present results on the exclusive nonleptonic and semileptonic decays of the B c-meson. The nonleptonic decays are studied in the framework of the factorization approximation. We calculate the branching ratios for a large set of exclusive nonleptonic and semileptonic decays of the B c meson and compare our results with the results of other models.

Radiative Decays of the P-Wave Charmed Mesons

1993

Minor (mainly numerical) corrections.

Cascade simulation of ultrarelativistic collisions

1988

The dynamics of hot matter produced in ultrarelativistic heavy-ion collisions is studied with a cascade simulation. We model the putative quark-gluon plasma with independent globs of high-density matter. The hadronic phase is treated by explicit tracking of pion coordinates. We find that the pions make 0--2 collisions with globs and 1--3 collisions with other pions, under conditions expected for heavy ions at collider energies. The entropy increases by about 20% during the phase transition. The transverse momentum in the final state is almost entirely due to the momentum with which pions are emitted from the globs, except at extremely high densities where the hydrodynamic expansion of the p…

Minimal Leptoquark Explanation for theRD(*),RK, and(g−2)μAnomalies

2016

We show that by adding a single new scalar particle to the standard model, a TeV-scale leptoquark with the quantum numbers of a right-handed down quark, one can explain in a natural way three of the most striking anomalies of particle physics: the violation of lepton universality in B[over ¯]→K[over ¯]l^{+}l^{-} decays, the enhanced B[over ¯]→D^{(*)}τν[over ¯] decay rates, and the anomalous magnetic moment of the muon. Constraints from other precision measurements in the flavor sector can be satisfied without fine-tuning. Our model predicts enhanced B[over ¯]→K[over ¯]^{(*)}νν[over ¯] decay rates and a new-physics contribution to B_{s}-B[over ¯]_{s} mixing close to the current central fit v…

Search for a Heavy Particle Decaying into an Electron and a Muon with the ATLAS Detector ins=7  TeVppcollisions at the LHC

2011

This Letter presents the first search for a heavy particle decaying into an e(+/-)mu(-/+) final state in root s = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95% confidence level are placed on two representative models. In an R-parity violating supersymmetric model, tau sneutrinos with a mass below 0.75 TeV are excluded, assuming all R-parity violating couplings are zero except lambda(311)' = 0.11 and lambda(312) = 0.07. In a lepton flavor violating model, a Z'-like vector boson with masses of 0.70-1.0…

Flavor Changing Yukawa Coupling in the Standard Model and Muon Polarization in KL-->mumu¯

1986

The muon longitudinal polarization P/sub L/ in K/sub L/..--> mu..mu-bar decay is investigated in the standard model. The induced s-bardH vertex responsible for P/sub L/ turns out to be unexpectedly ''large.'' The measurement of P/sub L/ above approx.10/sup -3/ will, therefore, be a signal of the existence of a rather light Higgs boson (M/sub H/< or approx. =10 GeV). It is also shown that the mechanism of gauge-dependence cancellation between Higgs-boson-exchange and box diagrams works even in the standard model.

DOUBLY CHARMED MESONS

2010

Doubly charmed mesons are studied within a quark model framework. We solve the four-quark Schor\"dinger equation by means of a variational approach by using different interacting potentials. Our results point to the existence of a stable isoscalar doubly charmed four-quark meson with quantum numbers $J^P=1^+$.

The Drell-Hearn-Gerasimov sum rule and the constituent quark model

1993

The helicity structure function of the nucleon has been calculated for the constituent quark model and compared to the prediction of the Drell-Hearn-Gerasimov sum rule. The multipole decomposition of the sum rule shows large cancellations between different resonances. The small isoscalar-isovector contribution is related to the admixture of aD-state (“bag deformation”) in the nucleon's wave function. The calculations indicate a relatively slow saturation of this part of the sum rule with excitation energy.

Double Pion Production Reactions

1999

We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent 2π photoproduction in nuclei are also reported.

Three pentaquark states or more?

2020