Search results for "DECAY"
showing 10 items of 2087 documents
Evidence forB0→ρ0ρ0Decays and Implications for the Cabibbo-Kobayashi-Maskawa Angleα
2007
We search for the decays B(0) --> rho(0)rho(0), B(0) --> rho(0)f(0)(980), and B(0) --> f(0)(980)f(0)(980) in a sample of about 384 x 10(6) Upsilon(4S) --> BB[over] decays collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) collider at Stanford Linear Accelerator Center. We find evidence for B(0) --> rho(0)rho(0) with 3.5 sigma significance and measure the branching fraction B = (1.07 +/- 0.33 +/- 0.19) x 10(-6) and longitudinal polarization fraction f(L) = 0.87 +/- 0.13 +/- 0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the Cabibbo-Kobayashi-Maskawa quark-mixing matrix unitarity angle alpha due to penguin contributio…
Semileptonic decays of double heavy baryons in a relativistic constituent three-quark model
2009
We study the semileptonic decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. We present complete results on transition form factors between double-heavy baryons for finite values of the heavy quark/baryon masses and in the heavy quark symmetry limit which is valid at and close to zero recoil. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit.
Rapidity distributions of dileptons from a hadronizing quark-gluon plasma
1994
It has been predicted that dilepton production may be used as a quark-gluon plasma probe. We calculate the rapidity distributions of thermal dileptons produced by an evolving quark-gluon plasma assuming a longitudinal scaling expansion with initial conditions locally determined from the hadronic rapidity density. These distributions are compared with Drell-Yan production and semileptonic charm decays at invariant mass $M = 2$, 4, and 6 GeV.
Heavy quark spin symmetry and heavy baryons: electroweak decays
2010
Heavy quark spin symmetry is discussed in the context of single and doubly heavy baryons. A special attention is paid to the constraints/simplifications that this symmetry imposes on the non-relativistic constituent quark model wave functions and on the b->c semileptonic decays of these hadrons.
Exclusive c → s, d Semileptonic Decays of Spin-1/2 and Spin-3/2 cb Baryons
2013
We present results for exclusive semileptonic decay widths of ground state spin-$1/2$ and spin-$3/2$ $cb$ baryons corresponding to a $c\to s, d$ transition at the quark level. The relevance of hyperfine mixing in spin-1/2 $cb$ baryons is shown. Our form factors are compatible with heavy quark spin symmetry constraints obtained in the infinite heavy quark mass limit.
Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb–Pb collisions at sNN=5.02 TeV
2020
The differential invariant yield as a function of transverse momentum (pT) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0–10%), semi-central (30–50%) and peripheral (60–80%) lead–lead (Pb–Pb) collisions at sNN=5.02 TeV in the pT intervals 0.5–26 GeV/c (0–10% and 30–50%) and 0.5–10 GeV/c (60–80%). The production cross section in proton–proton (pp) collisions at s=5.02 TeV was measured as well in 0.5<pT<10 GeV/c and it lies close to the upper band of perturbative QCD calculation uncertainties up to pT=5 GeV/c and close to the mean value for larger pT. The modification of the electron yield with respect to what is expected for an inco…
Hyperfine mixing in b -> c semileptonic decay of doubly heavy baryons
2010
We qualitatively corroborate the results of [W. Roberts, M. Pervin, Int. J. Mod. Phys. A 24 (2009) 2401] according to which hyperfine mixing greatly affects the decay widths of b -> c semileptonic decays involving doubly heavy bc baryons. However, our predictions for the decay widths of the unmixed states differ from those reported in the work of Roberts and Pervin by a factor of 2, and this discrepancy translates to the mixed case. We further show that the predictions of heavy quark spin symmetry, might be used in the future to experimentally extract information on the admixtures in the actual physical bc baryons, in a model independent manner.
Semileptonic decays of baryons containing two heavy quarks
1994
Abstract Semileptonic weak decays of doubly heavy baryons are analyzed and compared to the analogous decays of heavy quarkonia, showing similar underlying dynamics at low recoil.
Heavy Baryon Transitions in a Relativistic Three-Quark Model
1996
Exclusive semileptonic decays of bottom and charm baryons are considered within a relativistic three-quark model with a Gaussian shape for the baryon-three-quark vertex and standard quark propagators. We calculate the baryonic Isgur-Wise functions, decay rates and asymmetry parameters.
Renormalization of the effective theory for heavy quarks at small velocity
1995
The slope of the Isgur-Wise function at the normalization point, $\xi^{(1)}(1)$,is one of the basic parameters for the extraction of the $CKM$ matrix element $V_{cb}$ from exclusive semileptonic decay data. A method for measuring this parameter on the lattice is the effective theory for heavy quarks at small velocity $v$. This theory is a variant of the heavy quark effective theory in which the motion of the quark is treated as a perturbation. In this work we study the lattice renormalization of the slow heavy quark effective theory. We show that the renormalization of $\xi^{(1)}(1)$ is not affected by ultraviolet power divergences, implying no need of difficult non-perturbative subtraction…