5,089 research outputs found
Search for Anomaly at High x in Polarized Deep Inelastic Scattering Data
An idea of possible anomalous contribution of non-perturbative origin to the
nucleon spin was examined by analysing data on spin asymmetries in polarized
deep inelastic scattering of leptons on nucleons. The region of high Bjorken x
was explored. It was shown that experimental data available at present do not
evidence for this effect.Comment: Submitted to Mod.Phys.Lett.
On Neutrinos and Fermionic Mass Patterns
Recent data on neutrino mass differences are consistent with a hierarchical
neutrino mass structure strikingly similar to what is observed for the other
fermionic masses.Comment: 8pages, 2figure
Sparticle Mass Spectrum in Grand Unified Theories
We carry out a detailed analysis of sparticle mass spectrum in supersymmetric
grand unified theories. We consider the spectroscopy of the squarks and
sleptons in SU(5) and SO(10) grand unified theories, and show how the
underlying supersymmetry breaking parameters of these theories can be
determined from a measurement of different sparticle masses. This analysis is
done analytically by integrating the one-loop renormalization group equations
with appropriate boundary conditions implied by the underlying grand unified
gauge group. We also consider the impact of non-universal gaugino masses on the
sparticle spectrum, especially the neutralino and chargino masses which arise
in supersymmetric grand unified theories with non-minimal gauge kinetic
function. In particular, we study the interrelationships between the squark and
slepton masses which arise in grand unified theories at the one-loop level,
which can be used to distinguish between the different underlying gauge groups
and their breaking pattern to the Standard Model gauge group. We also comment
on the corrections that can affect these one-loop results.Comment: 19 pages, 6 figure
Fermion mass hierarchy and non-hierarchical mass ratios in SU(5) x U(1)_F
We consider a SU(5) x U(1)_F GUT-flavor model in which the number of effects
that determine the charged fermions Yukawa matrices is much larger than the
number of observables, resulting in a hierarchical fermion spectrum with no
particular regularities. The GUT-flavor symmetry is broken by flavons in the
adjoint of SU(5), realizing a variant of the Froggatt-Nielsen mechanism that
gives rise to a large number of effective operators. By assuming a common mass
for the heavy fields and universality of the fundamental Yukawa couplings, we
reduce the number of free parameters to one. The observed fermion mass spectrum
is reproduced thanks to selection rules that discriminate among various
contributions. Bottom-tau Yukawa unification is preserved at leading order, but
there is no unification for the first two families. Interestingly, U(1)_F
charges alone do not determine the hierarchy, and can only give upper bounds on
the parametric suppression of the Yukawa operators.Comment: 14 pages, one figure. Few typos correcte
The exact eigenstates of the neutrino mass matrix without CP-phase violation
In this paper we obtain the exact mass-eigenstates of the Majorana physical
neutrinos. We start by taking into account a general mass matrix
without any CP-phase violation. It is then diagonalized by exactly solving an
appropriate set of equations. The solution supplies straightforwardly the mass
eigenvalues depending on the diagonal entries and mixing angles. Finally, the
consequences of these analytical expressions are discussed assuming various
phenomenological restrictions such as conserving the global lepton number
and the interchange symmetry. The minimal
absolute mass in the neutrino sector is also obtained since the two plausible
scenarios invoked above are employed.Comment: 9 pages, no figure
The Inclusive Semileptonic Decay Lepton Spectrum from
In this talk, we review the QCD calculation of the lepton spectrum from
inclusive semileptonic decay. We compare this prediction to that of the
ACCMM model. This latter work was done in collaboration with Csaba Csaki.Comment: MIT-CTP-2333, uses LATEX. Invited Talk, Presented at WHEPP-3 Workshop
in Madras,India, January, 199
Heavy Quark Lifetimes, Mixing and CP Violation
This paper emphasizes four topics that represent some of the year's
highlights in heavy quark physics. First of all, a review is given of charm
lifetime measurements and how they lead to better understanding of the
mechanisms of charm decay. Secondly, the CLEO collaboration's new search for
charm mixing is reported, which significantly extends the search for new
physics in that sector. Thirdly, important updates in Bs mixing are summarized,
which result in a new limit on the mass difference, and which further constrain
the unitarity triangle. Finally, the first efforts to measure CP violation in
the B system are discussed. Results are shown for the CDF and ALEPH
measurements of sin(2beta), as well as the CLEO branching fraction measurements
of B-->Kpi,pipi, which have implications for future measurements of alpha.Comment: 25 pages, 15 figures. Talk given at the XIX International Symposium
on Lepton and Photon Interactions, Stanford University, August 9-14, 199
Probing Electroweak Top Quark Couplings at Hadron Colliders
We consider QCD t\bar{t}\gamma and t\bar{t}Z production at hadron colliders
as a tool to measure the tt\gamma and ttZ couplings. At the Tevatron it may be
possible to perform a first, albeit not very precise, test of the tt\gamma
vector and axial vector couplings in t\bar{t}\gamma production, provided that
more than 5 fb^{-1} of integrated luminosity are accumulated. The t\bar{t}Z
cross section at the Tevatron is too small to be observable. At the CERN Large
Hadron Collider (LHC) it will be possible to probe the tt\gamma couplings at
the few percent level, which approaches the precision which one hopes to
achieve with a next-generation e^+e^- linear collider. The LHC's capability of
associated QCD t\bar{t}V (V=\gamma, Z) production has the added advantage that
the tt\gamma and ttZ couplings are not entangled. For an integrated luminosity
of 300 fb^{-1}, the ttZ vector (axial vector) coupling can be determined with
an uncertainty of 45-85% (15-20%), whereas the dimension-five dipole form
factors can be measured with a precision of 50-55%. The achievable limits
improve typically by a factor of 2-3 for the luminosity-upgraded (3 ab^{-1})
LHC.Comment: Revtex3, 30 pages, 9 Figures, 6 Table
Vacuum Alignment in SUSY A4 Models
In this note we discuss the vacuum alignment in supersymmetric models with
spontaneously broken flavour symmetries in the presence of soft supersymmetry
(SUSY) breaking terms. We show that the inclusion of soft SUSY breaking terms
can give rise to non-vanishing vacuum expectation values (VEVs) for the
auxiliary components of the flavon fields. These non-zero VEVs can have an
important impact on the phenomenology of this class of models, since they can
induce an additional flavour violating contribution to the sfermion soft mass
matrix of right-left (RL) type. We carry out an explicit computation in a class
of SUSY A4 models predicting tri-bimaximal mixing in the lepton sector. The
flavour symmetry breaking sector is described in terms of flavon and driving
supermultiplets. We find non-vanishing VEVs for the auxiliary components of the
flavon fields and for the scalar components of the driving fields which are of
order m_{SUSY} x and m_{SUSY}, respectively. Thereby, m_{SUSY} is the
generic soft SUSY breaking scale which is expected to be around 1 TeV and
is the VEV of scalar components of the flavon fields. Another effect of these
VEVs can be the generation of a mu term.Comment: 23 pages; added a new section on the relation to Supergravity;
version accepted for publication in JHE
Polarized Deeply Inelastic Scattering (DIS) Structure Functions for Nucleons and Nuclei
We extract parton distribution functions (PDFs) and structure functions from
recent experimental data of polarized lepton-DIS on nucleons at next-to-leading
order (NLO) Quantum Chromodynamics. We apply the Jacobi polynomial method to
the DGLAP evolution as this is numerically efficient. Having determined the
polarized proton and neutron spin structure, we extend this analysis to
describe 3He and 3H polarized structure functions, as well as various sum
rules. We compare our results with other analyses from the literature.Comment: LaTeX, 12 pages, 11 figures, 6 tables. Update to match published
versio
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