487 research outputs found
Fit to Moments of Inclusive B->Xc lv and B-> Xs gamma Decay Distributions using Heavy Quark Expansions in the Kinetic Scheme
We present a fit to measured moments of inclusive distributions in B->Xc lv
and B-> Xs gamma decays to extract values for the CKM matrix element |Vcb|, the
b- and c-quark masses, and higher order parameters that appear in the Heavy
Quark Expansion. The fit is carried out using theoretical calculations in the
kinetic scheme and includes moment measurements of the Babar, Belle, CDF, CLEO
and DELPHI collaborations for which correlation matrices have been published.
We find |Vcb| = (41.96 +- 0.23(exp) +- 0.35(HQE) +- 0.59(Gamma_SL)) 10^-3 and
m_b = 4.590 +- 0.025(exp) +- 0.30(HQE) GeV where errors are experimental and
theoretical respectively. We also derive values for the heavy quark
distribution function parameters m_b and \mu_\pi^2 in different theoretical
schemes that can be used as input for the determination of |Vub|.Comment: 13 pages, 6 figures. v3: Fig 1+2 show absolute values for moments and
fit rather than the difference. Updated some references. v2: Updated to
include Belle photon moments and PDG 2005 lifetime. Included extrapolation
factors for the BR(B->Xs gamma) to 1.6 Gev based on the HQE parameters from
the fit and added an updated OPE expression for |Vub
Signals for Vector Leptoquarks in Hadronic Collisions
We analyze systematically the signatures of vector leptoquarks in hadronic
collisions. We examine their single and pair productions, as well as their
effects on the production of lepton pairs. Our results indicate that a machine
like the CERN Large Hadron Collider (LHC) will be able to unravel the existence
of vector leptoquarks with masses up to the range of -- TeV.Comment: 15 pages and 5 figures (available upon request or through anonymous
ftp), revtex3, IFUSP-P 108
Leptogenesis with "Fuzzy Mass Shell" for Majorana Neutrinos
We study the mixing of elementary and composite particles. In quantum field
theory the mixing of composite particles originates in the couplings of the
constituent quarks and for neutrinos in self-energy diagrams. In the event that
the incoming and outgoing neutrinos have different masses, the self-energy
diagrams vanish because energy is not conserved but the finite decaying widths
make the mixing possible. We can consider the neutrinos to be "fuzzy" states on
their mass shell and the mixing is understood as the overlap of two
wavefunctions. These considerations restrict the mass difference to be
approximately equal to or smaller than the largest of the two widths: abs(M_i -
M_j) lessorequal max(Gamma_i, Gamma_j).Comment: 11 pages, 1 figur
Single Leptoquark Production at and Colliders
We consider single production of leptoquarks (LQ's) at and
colliders, for two values of the centre-of-mass energy,
GeV and 1 TeV. We find that LQ's which couple within the first
generation are observable for LQ masses almost up to the kinematic limit, both
at and colliders, for the LQ coupling strength equal to
. The cross sections for single production of - and
-generation LQ's at colliders are too small to be observable.
In collisions, on the other hand, -generation LQ's with
masses much larger than can be detected. However,
-generation LQ's can be seen at colliders only for
masses at most , making their observation more probable via the
pair production mechanism.Comment: plain TeX, 14 pages, 6 figures (not included but available on
request), some minor changes to the text, one reference added, figures and
conclusions unchanged, UdeM-LPN-TH-93-152, McGill-93/2
Signal and Backgrounds for Leptoquarks at the LHC
We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel
the existence of first generation scalar leptoquarks.
Working with the most general invariant leptoquark
interactions, we analyze in detail the signals and backgrounds that lead to a
final state containing a pair and jets. Our results indicate that a
machine like the LHC will be able to discover leptoquarks with masses up to
2--3 TeV depending on their couplings.Comment: 37 pages, revtex, uses epsfig.sty (included), 15 figures (included
Signal and Backgrounds for Leptoquarks at the LHC II: Vector Leptoquarks
We perform a detailed analyses of the CERN Large Hadron Collider (LHC)
capability to discover first generation vector leptoquarks through their pair
production. We study the leptoquark signals and backgrounds that give rise to
final states containing a pair e+e- and jets. Our results show that the LHC
will be able to discover vector leptoquarks with masses up to 1.3-2.1 TeV
depending on their couplings to fermions and gluons.Comment: 18 pages, 3 figures, REVTe
The Singlet Majoron Model with Hidden Scale Invariance
We investigate an extension of the Singlet Majoron Model in which the
breaking of dilatation symmetry by the mass parameters of the scalar potential
is removed by means of a dilaton field. Starting from the one-loop
renormalization group improved potential, we discuss the ground state of the
theory. The flat direction in the classical potential is lifted by quantum
corrections and the true vacua are found. Studying the finite temperature
potential, we analyze the cosmological consequences of a Jordan-Brans-Dicke
dilaton and show that the lepton number is spontaneously broken after the
electroweak phase transition, thus avoiding any constraint coming from the
requirement of the preservation of the baryon asymmetry in the early Universe.
We also find that, contrary to the Standard Model case, the dilaton cosmology
does not impose any upper bound on the scale of the spontaneous breaking of
scale invariance.Comment: 22 pages, SISSA-5/93/A and DFPD/93/TH/0
Signal and Backgrounds for the Single Production of Scalar and Vector Leptoquarks at the LHC
We perform a detailed analysis of the potentiality of the CERN Large Hadron
Collider to study the single production of leptoquarks via
leptoquark , with generated by the splitting of photons
radiated by the protons. Working with the most general
invariant effective lagrangian for scalar and vector leptoquarks, we analyze in
detail the leptoquark signals and backgrounds that lead to a final state
containing an and a hard jet with approximately balanced transverse
momenta. Our results indicate that the LHC will be able to discover leptoquarks
with masses up to 2--3 TeV, depending on their type, for Yukawa couplings of
the order of the electromagnetic one.Comment: Revtex, 23 pages, 11 postscript files. Uses axodraw.sty (included)
and epsfig.sty. Typos corrected. To be published in Phys. Rev.
Multilepton Signatures for Leptoquarks
The production of third generation leptoquarks can give rise to multilepton
events accompanied by jets and missing transverse energy.
In this work we study the signals of these leptoquarks at the CERN Large
Hadron Collider and compare them with the ones expected in supersymmetric
models.Comment: 13 pages, 4 figure
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