Prospects for the extraction of ∣Vcb∣{\mid}V_{cb}{\mid} from $B_c\ {\to}\ J/\psi\ {\mu}^+\ {\nu}$ decays at LHC

We discuss the possibility of extracting ${\mid}V_{cb}{\mid}$ from the future measurement at LHC of the $B_c\ {\rightarrow}\ J/\psi\ {\mu}^+\ {\nu}$ decay rate followed by the leptonic decay $J/\psi\ {\rightarrow}\ \mu^+\mu^-$. We examine in detail the influence of the measurement of the muons' momenta and vertex reconstruction in the final uncertainty of ${\mid}V_{cb}{\mid}$, as well as the required theoretical inputs at both the production and weak decay level, and their reliability in this regard. We stress the relevance of a rigorous description of the fragmentation contributions to inclusive production at large transverse momentum of heavy quarkonia in $pp$ collisions.Comment: Latex using psfig.sty, 19 pages including 9 uuencoded. Replaced because of a few missprint error

Bethe-Salpeter equation for doubly heavy baryons in the covariant instantaneous approximation

In the heavy quark limit, a doubly heavy baryon is regarded as composed of a heavy diquark and a light quark. We establish the Bethe-Salpeter (BS) equations for the heavy diquarks and the doubly heavy baryons, respectively, to leading order in a $1/m_{Q}$ expansion. The BS equations are solved numerically under the covariant instantaneous approximation with the kernels containing scalar confinement and one-gluon-exchange terms. The masses for the heavy diquarks and the doubly heavy baryons are obtained and the non-leptonic decay widths for the doubly heavy baryons emitting a pseudo-scalar meson are calculated within the model.Comment: Corrections to the text, two references added, version accepted for publication in Physical Review

Power scaling rules for charmonia production and HQEFT

We discuss the power scaling rules along the lines of a complete Heavy Quark Effective Field Theory (HQEFT) for the description of heavy quarkonium production through a color-octet mechanism. To this end, we firstly derive a tree-level heavy quark effective Lagrangian keeping both particle-antiparticle mixed sectors allowing for heavy quark-antiquark pair annihilation and creation, but describing only low-energy modes around the heavy quark mass. Then we show the consistency of using HQEFT fields in constructing four-fermion local operators a la NRQCD, to be identified with standard color-octet matrix elements. We analyze some numerical values extracted from charmonia production by different authors and their hierarchy in the light of HQEFT.Comment: LaTeX, 19 pages, 3 EPS figure

A heavy quark effective field lagrangian keeping particle and antiparticle mixed sectors

We derive a tree-level heavy quark effective Lagrangian keeping particle-antiparticle mixed sectors allowing for heavy quark-antiquark pair annihilation and creation. However, when removing the unwanted degrees of freedom from the effective Lagrangian one has to be careful in using the classical equations of motion obeyed by the effective fields in order to get a convergent expansion on the reciprocal of the heavy quark mass. Then the application of the effective theory to such hard processes should be sensible for special kinematic regimes as for example heavy quark pair production near threshold.Comment: LaTeX, 14 pages, 1 EPS figure

Leptonic universality breaking in Upsilon decays as a probe of new physics

In this work we examine the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the $B\bar{B}$ threshold. The decay width is factorized as the product of two pieces: a) the probability of an intermediate pseudoscalar color-singlet $b\bar{b}$ state (coupling to the dominant Fock state of the Upsilon via a magnetic dipole transition) and a soft (undetected) photon; b) the annihilation width of the $b\bar{b}$ pair into two leptons, mediated by a non-standard CP-odd Higgs boson of mass about 10 GeV, introducing a quadratic dependence on the lepton mass in the partial width. The process would be unwittingly ascribed to the $\Upsilon$ leptonic channel thereby (slightly) breaking lepton universality. A possible mixing of the pseudoscalar Higgs and bottomonium resonances is also considered. Finally, several experimental signatures to check out the validity of the conjecture are discussed.Comment: LaTeX, 22 pages, 2 EPS figure

Indirect detection of light neutralino dark matter in the NMSSM

We explore the prospects for indirect detection of neutralino dark matter in supersymmetric models with an extended Higgs sector (NMSSM). We compute, for the first time, one-loop amplitudes for NMSSM neutralino pair annihilation into two photons and two gluons, and point out that extra diagrams (with respect to the MSSM), featuring a potentially light CP-odd Higgs boson exchange, can strongly enhance these radiative modes. Expected signals in neutrino telescopes due to the annihilation of relic neutralinos in the Sun and in the Earth are evaluated, as well as the prospects of detection of a neutralino annihilation signal in space-based gamma-ray, antiproton and positron search experiments, and at low-energy antideuteron searches. We find that in the low mass regime the signals from capture in the Earth are enhanced compared to the MSSM, and that NMSSM neutralinos have a remote possibility of affecting solar dynamics. Also, antimatter experiments are an excellent probe of galactic NMSSM dark matter. We also find enhanced two photon decay modes that make the possibility of the detection of a monochromatic gamma-ray line within the NMSSM more promising than in the MSSM.Comment: 26 pages, 12 figures. Updated references and corrected discussion of Upsilon decay

Two-particle angular correlations in the search for new physics at future e+e−e^+e^- colliders

The analysis of angular particle correlations can yield valuable insights into the initial state of matter in high-energy collisions, thereby potentially revealing the existence of Beyond the Standard Model scenarios such as Hidden Valley (HV). In this study, we focus on a QCD-like hidden sector with relatively massive HV quarks ($\lesssim 100$~GeV) which might enlarge and strengthen azimuthal correlations of final-state SM hadrons. In particular, we study the formation and possible observation of \textit{ridge-like} structures in the angular two-particle correlation function at future $e^+e^-$ colliders, with a much cleaner environment than in hadron colliders, such as the LHC.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS 2023), 15-19 May 2023. C23-05-15.

High-pTp_T ψψ\psi\psi production as signals for Double Parton scattering at hadron colliders

We present an analysis of the \psi\psi production from double parton (DP) sacttering and single parton (SP) scattering in the large p_T region via color-octet gluon fragmentation. We find that at the Tevatron the DP \psi\psi production is at the edge of the detectability at present, and at the LHC the DP cross section will dominate over the SP cross section in the lower p_T(min) region (i.e., p_T(min)<7GeV). We also conclude that the color-octet mechanism is of crucial importance to the double j/psi production at high energy hadron colliders.Comment: Revtex, 12 pages, 3 Postscript figure