118594300
Phenomenological study of the $B_{c}$ ${\to}$ $BP$, $BV$ decays with perturbative QCD approach
Inspired by the recent LHCb measurements and forthcoming great potential on $B_{c}$ meson, we study the exclusive $B_{c}$ ${\to}$ $B_{q}P$, $B_{q}V$ decays with the perturbative QCD approach, where $q$ $=$ $u$, $d$, $s$; $P$ and $V$ denote the lightest pseudoscalar and vector $SU(3)$ nonet meson, respectively. By retaining the quark transverse momentum, employing the Sudakov factors, and choosing the typical scale as the maximum virtualities of the internal particles, we calculate the $B_{c}$ ${\to}$ $B$ transition from factors, and our results show that about 90\% contribution to form factors come from the ${\alpha}_{s}/{\pi}$ $<$ $0.3$ region. The contributions of penguin and annihilation to branching ratios are very small due to the serious suppression by the CKM factors. There is some hierarchy relations among the $B_{c}$ ${\to}$ $BP$, $BV$ decays. The branching ratios for $B_{c}$ ${\to}$ $B_{d,s}{\pi}$, $B_{d,s}{\rho}$, $B_{s}K$ are large and could be measured by the running LHCb.
14205678
Phenomenological analysis of B -> PP decays with QCD factorization
In this paper, we study nonleptonic charmless B decays to two light pseudoscalar mesons within the frame of QCD factorization, including the contributions from the chirally enhanced power corrections and weak annihilation. Predictions for the CP-averaged branching ratios and CP-violating asymmetries are given. Within the reasonable range of the parameters, we find that our predictions for the branching ratios of B-->PP are consistent with the present experimental data. But because of the logarithmic divergences at the end points in the hard spectator scatterings and weak annihilation, there are still large uncertainties in these predictions.
119214722
Study on the properties of the coupling constants of $J/\psi \rightarrow VP$ decays
Basing on the branching fractions of J/\psi \to VP from different experiments, we investigate on the properties of the coupling constants of J/\psi \to VP decays with a model-dependent approach. We find that the octet coupling constant, g_8, of strong interaction is about twice larger than that of the singlet coupling constant g_1; the electromagnetic breaking parameters g^i_E are larger than the mass breaking parameters g^i_M, moreover, the three parameters of electromagnetic effect are about equal, but the three parameters of mass effect are obviously different and their uncertainties are also large; and the phase angle between strong and electromagnetic interaction is in the range of 70^{\circ} \sim 80^{\circ}. It deepens our understanding of the coupling constant of J/\psi \to VP decays.
123690941
Pseudo-Goldstone boson corrections to top-quark production at the Fermilab Tevatron in a topcolour-assisted multiscale technicolour model
Using a topcolour-assisted multiscale technicolour model, we calculate the corrections of pseudo-Goldstone bosons (technipions, top pions) to the cross section of the process q→t at the Fermilab Tevatron. Our results show that corrections mainly come from top pions. With reasonable values of the parameters, the correction can increase the total t production cross section σt by as much as 17%. This may provide a window to detect top pions.
55380857
Mimic the optical conductivity in disordered solids via gauge/gravity duality ✩
Abstract We study the optical conductivity in a ( 2 + 1 ) -dimensional non-relativistic field theory holographically dual to a ( 3 + 1 ) -dimensional charged Lifshitz black brane within the Einstein–Maxwell-dilaton theory. Surprisingly, we find that the optical AC conductivity satisfies the nontrivial (non-)power law scaling in the high frequency regime rather than approaching to a constant when the dynamical critical exponent z > 1 , which is qualitatively similar to those in various disordered solids in condensed matter systems. Besides, this (non-)power law scaling behavior shows some universality, which is robust against the temperatures. We argue that the peculiar scaling behavior of AC conductivity may stem from the couplings of the dilaton field with the gauge fields and also the logarithmic behavior near the boundary in the Lifshitz spacetime.
119212173
Note on Chern-Simons term correction to holographic entanglement entropy
From the perspective of AdS/CFT correspondence, we study the gravitational Chern-Simons term correction to the holographic entanglement entropy of CFT on the conformal boundary of asymptotically AdS3 spacetime using the off-shell Euclidean path integral method. We show that, like the BTZ black hole entropy, the holographic entanglement entropy is indeed modified due to the gravitational Chern-Simons term although the bulk geometry does not change.
119264101
Novel features of the transport coefficients in Lifshitz black branes
We study the transport coefficients, including the conductivities and shear viscosity of the non-relativistic field theory dual to the Lifshitz black brane with multiple U(1) gauge fields by virtue of the gauge/gravity duality. Focusing on the case of double U(1) gauge fields, we systematically investigate the electric, thermal and thermoelectric conductivities for the dual non-relativistic field theory. In the large frequency regime, we find a nontrivial power law behavior in the electric AC conductivity when the dynamical critical exponent z>1 in (2+1)-dimensional field theory. The relations between this novel feature and the `symmetric hopping model' in condensed matter physics are discussed. In addition, we also show that the Kovtun-Starinets-Son bound for the shear viscosity to the entropy density is not violated by the additional U(1) gauge fields and dilaton in the Lifshitz black brane.
118555844
Holographic dual of the dyonic Reissner-Nordström black hole
It is shown that the hidden conformal symmetry, namely SO(2,2) ∼ SL(2,R)L × SL(2,R)R symmetry, of the non-extremal dyonic Reissner-Nordstrblack hole can be probed by a charged massless scalar field at low frequencies. The existence of such hidden conformal symmetry suggests that the field theory holographically dual to the 4D Reissner-Nordstrom black hole indeed should be a 2D CFT. Although the associated AdS3 structure does not explicitly appear in the near horizon geometry, the primary parameters of the dual CFT2 can be exactly obtained without the necessity of embedding the 4D Reissner-Nordstrblack hole into 5D spacetime. The duality is further supported by comparing the absorption cross sections and real-time correlators obtained from both the CFT and the gravity sides.
55522246
COURANT-SNYDER INVARIANT DENSITY SCREENING METHOD FOR EMITTANCE ANALYSIS *
The emittance is an important characteristic of describing charged particle beams. In hadron accelerators, we often meet irregular beam distributions that are not appropriate to be described with a single rms emittance or 95% emittance or total emittance. In this paper, it is pointed out that in many cases beam halo should be described with very different Courant-Snyder parameters from the ones for beam core. A new method – CourantSnyder invariant density screening method is introduced for analyzing emittance data clearly and accurately.