22,110 research outputs found
Gell-Mann--Okubo Mass Formula for an SU(4) Meson Hexadecuplet
Using a linear mass spectrum of an meson hexadecuplet, we derive the
Gell-Mann--Okubo mass formula for the charmed mesons, in good agreement with
experiment. Possible generalization of this method to a higher symmetry group
is briefly discussed.Comment: 11 pages, LaTe
Dynamical Generation of Linear model SU(3) Lagrangian and Meson Nonet Mixing
This paper is the SU(3) extension of the dynamically generated SU(2) linear
model Lagrangian worked out previously using dimensional
regularization. After discussing the quark-level Goldberger-Treiman relations
for SU(3) and the related gap equations, we dynamically generate the meson
cubic and quartic couplings. This also constrains the meson-quark coupling
constant to and determines the SU(3) scalar meson masses in a
Nambu-Jona-Lasinio fashion. Finally we dynamically induce the U(3) pseudoscalar
and scalar mixing angles in a manner compatible with data.Comment: 19 printed pages, requires plain Tex, now published in IJMPA 13, 657
(1998
Non-functional immunoglobulin G transcripts in a case of hyper-immunoglobulin M syndrome similar to type 4
86% of immunoglobulin G (IgG) heavy-chain gene transcripts were found to be non-functional in the peripheral blood B cells of a patient initially diagnosed with common variable immunodeficiency, who later developed raised IgM, whereas no non-functionally rearranged transcripts were found in the cells of seven healthy control subjects. All the patient's IgM heavy-chain and κ light-chain transcripts were functional, suggesting that either non-functional rearrangements were being selectively class-switched to IgG, or that receptor editing was rendering genes non-functional after class-switching. The functional γ-chain sequences showed a normal rate of somatic hypermutation while non-functional sequences contained few somatic mutations, suggesting that most came from cells that had no functional gene and therefore were not receiving signals for hypermutation. However, apoptosis of peripheral blood lymphocytes was not impaired. No defects have been found in any of the genes currently known to be responsible for hyper-IgM syndrome but the phenotype fits best to type 4
Theoretical aspects of high--Q^2 deep inelastic scattering
We present an overview of the theory of high--Q^2 deep inelastic scattering.
We focus in particular on the theoretical uncertainties in the predictions for
neutral and charged current cross sections obtained by extrapolating from lower
Q^2.Comment: 10 (Latex) pages, including 6 embedded figures, uses epsfig.sty,
ioplppt.sty and iopl12.sty; Plenary talk presented at the 3rd UK
Phenomenology Workshop on HERA Physics, Durham, September 1998, to be
published in the Proceeding
Joint teleconsultations (virtual outreach) versus standard outpatient appointments for patients referred by their general practitioner for a specialist opinion: a randomised trial.
BACKGROUND: The current model of general practitioner referral of patients to hospital specialists in the UK is sometimes associated with unnecessary duplication of investigations and treatments. We aimed to compare joint teleconsultations between general practitioners, specialists, and patients (virtual outreach) with standard outpatient referral. METHODS: Virtual outreach services were established in London and Shrewsbury. The general practitioners referred 3170 patients, of whom 2094 consented to participate in the study and were eligible for inclusion. 1051 patients were randomly assigned virtual outreach, and 1043 standard outpatient appointments. We followed up the patients for 6 months after their index consultation. The primary outcome measure was the offer of a follow-up outpatient appointment. Analysis was by intention to treat. FINDINGS: More patients in the virtual outreach group than the standard group were offered a follow-up appointment (502 [52%] vs 400 [41%], odds ratio 1.52 [95% CI 1.27-1.82], p<0.0001). Significant differences in effects were observed between the two sites (p=0.009) and across different specialties (p<0.0001). Virtual outreach increased the offers of follow-up appointments more in Shrewsbury than in London, and more in ear, nose, and throat surgery and orthopaedics than in the other specialties. Fewer tests and investigations were ordered in the virtual outreach group by an average of 0.79 per patient (0.37-1.21, p=0.0002). Patients' satisfaction (analysed per protocol) was greater after a virtual outreach consultation than after a standard outpatient consultation (mean difference 0.33 scale points [95% CI 0.23-0.43], p<0.0001), with no heterogeneity between specialties or sites. INTERPRETATION: The trial showed that allocation of patients to virtual outreach consultations is variably associated with increased offers of follow-up appointments according to site and specialty, but leads to significant increases in patients' satisfaction and substantial reductions in tests and investigations. Efficient operation of such services will require appropriate selection of patients, significant service reorganisation, and provision of logistical support
A simple quantum cosmology
A simple and surprisingly realistic model of the origin of the universe can
be developed using the Friedmann equation from general relativity, elementary
quantum mechanics, and the experimental values of h, c, G and the proton mass.
The model assumes there are N space dimensions (with N > 6) and the potential
constraining the radius r of the invisible N -3 compact dimensions varies as
r^4. In this model, the universe has zero total energy and is created from
nothing. There is no initial singularity. If space-time is eleven dimensional,
as required by M theory, the scalar field corresponding to the size of the
compact dimensions inflates the universe by about 26 orders of magnitude (60
e-folds). If the Hubble constant is 65 km/sec Mpc, the energy density of the
scalar field after inflation results in Omega-sub-Lambda = 0.68, in agreement
with recent astrophysical observations.Comment: To be published in General Relativity and Gravitation, August 200
The dispersive contribution of decays and X(1576)
We study whether the broad enhancement X(1576) arises from the final state
interaction (FSI) of decays. We
consider both the absorptive and dispersive contribution of the above
amplitudes since the intermediate states are very close to .
The same mechanism leads to a similar enhancement around 1580 MeV in the
spectrum in the channel, which
can be used to test whether X(1576) can be ascribed to the FSI effect of
.Comment: 4 pages, 4 figure
Cosmological implications of the Higgs mass measurement
We assume the validity of the Standard Model up to an arbitrary high-energy
scale and discuss what information on the early stages of the Universe can be
extracted from a measurement of the Higgs mass. For Mh < 130 GeV, the Higgs
potential can develop an instability at large field values. From the absence of
excessive thermal Higgs field fluctuations we derive a bound on the reheat
temperature after inflation as a function of the Higgs and top masses. Then we
discuss the interplay between the quantum Higgs fluctuations generated during
the primordial stage of inflation and the cosmological perturbations, in the
context of landscape scenarios in which the inflationary parameters scan. We
show that, within the large-field models of inflation, it is highly improbable
to obtain the observed cosmological perturbations in a Universe with a light
Higgs. Moreover, independently of the inflationary model, the detection of
primordial tensor perturbations through the B-mode of CMB polarization and the
discovery of a light Higgs can simultaneously occur only with exponentially
small probability, unless there is new physics beyond the Standard Model.Comment: 28 LaTeX pages, 6 figure
Constraints on Supersymmetric Flavour Models from b->s gamma
We consider the effects of departures from minimal flavour violations (MFV)
in the context of CMSSM-like theories. Second and third generation off-diagonal
elements in the Yukawa, sfermion, and trilinear mass matrices are taken to be
non-zero at the GUT scale. These are run down together with MSSM parameters to
the electroweak scale. We apply constraints from fermion masses and CKM matrix
elements to limit the range of the new free parameters of the model. We
determine the effect of the departure from MFV on the branching ratio of b->s
gamma. We find that only when the expansion parameter in the down-squark sector
is relatively large there is a noticeable effect, which tends to relax the
lower limit from b->s gamma on the universal gaugino mass. We also find that
the expansion parameter associated with the slepton sector needs to be smaller
than the corresponding parameter in the down-squark sector in order to be
compliant with the bound imposed by the branching ratio of tau-> mu gamma.Comment: Comments: 43 pages, 14 figures. Version accepted for publication:
typos corrected, rewritten for better understanding and references adde
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