1,331 research outputs found
Semi-naive dimensional renormalization
We propose a treatment of in dimensional regularization which is
based on an algebraically consistent extension of the Breitenlohner-Maison-'t
Hooft-Veltman (BMHV) scheme; we define the corresponding minimal
renormalization scheme and show its equivalence with a non-minimal BMHV scheme.
The restoration of the chiral Ward identities requires the introduction of
considerably fewer finite counterterms than in the BMHV scheme. This scheme is
the same as the minimal naive dimensional renormalization in the case of
diagrams not involving fermionic traces with an odd number of , but
unlike the latter it is a consistent scheme. As a simple example we apply our
minimal subtraction scheme to the Yukawa model at two loops in presence of
external gauge fields.Comment: 28 pages, 3 figure
Large Universality of The Baryon Isgur--Wise Form Factor: The Group Theoretical Approach
In a previous article, it has been proved under the framework of chiral
soliton model that the same Isgur--Wise form factor describes the semileptonic
and decays in the
large limit. It is shown here that this result is in fact independent of
the chiral soliton model and is solely the consequence of the spin-flavor SU(4)
symmetry which arises in the baryon sector in the large limit.Comment: 10 pages in REVTeX, no figure
Amplitude analysis of hadron decays
We provide succinct covariant amplitude decompositions of 2-body weak
hadronic decays, with which to compare data, including exclusive rates,
helicity amplitudes and polarizations. For weak decays, the systematic
dependence of these amplitudes on masses and quantum numbers of participating
particles are determined within a factor of about two by the CKM angles and the
Fermi constant so theoretical models need to be much more accurate if they are
to be convincing.Comment: 31 pages, RevTe
Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays
In the semileptonic decays of heavy mesons and baryons, the lepton-mass dependence factors out in the quadratic cos2θ coefficient of the differential cosθ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor, and restricting the phase space integration to the τ lepton phase space, one can define optimized partial rates which, in the Standard Model, are the same for all three (e,μ,τ) modes in a given semileptonic decay process. We discuss how the identity is spoiled by new physics effects. We discuss semileptonic heavy meson decays such as B¯0→D(∗)+ℓ-ν¯ℓ and Bc-→J/ψ(ηc)ℓ-ν¯ℓ and semileptonic heavy baryon decays such as Λb→Λcℓ-ν¯ℓ for each ℓ=e, μ, τ
Exclusive semileptonic decays of D and Ds mesons in the covariant confining quark model
Recently, the BESIII collaboration has reported numerous measurements of various D(s) meson
semileptonic decays with significantly improved precision. Together with similar studies carried out at
BABAR, Belle, and CLEO, new windows to a better understanding of weak and strong interactions
in the charm sector have been opened. In light of new experimental data, we review the theoretical
description and predictions for the semileptonic decays of D(s) to a pseudoscalar or a vector meson.
This review is essentially an extended discussion of our recently published results obtained in the
framework of the covariant confining quark model
Spectral fluctuation characterization of random matrix ensembles through wavelets
A recently developed wavelet based approach is employed to characterize the
scaling behavior of spectral fluctuations of random matrix ensembles, as well
as complex atomic systems. Our study clearly reveals anti-persistent behavior
and supports the Fourier power spectral analysis. It also finds evidence for
multi-fractal nature in the atomic spectra. The multi-resolution and
localization nature of the discrete wavelets ideally characterizes the
fluctuations in these time series, some of which are not stationary.Comment: 7 pages, 2 eps figure
Importance of Tests for the Complete Lorentz Structure of the t --> W+ b vertex at Hadron Colliders
The most general Lorentz-invariant decay-density-matrix for , or for , is expressed in terms
of eight helicity parameters. The parameters are physically defined in terms of
partial-width-intensities for polarized-final-states in decay.
The parameters are the partial width, the quark's chirality parameter
, the polarimetry parameter , a "pre-SSB" test parameter
, and four - interference parameters , ,
, which test for violation. They can be
used to test for non-CKM-type CP violation, anomalous 's, top
weak magnetism, weak electricity, and second-class currents. By stage-two
spin-correlation techniques, percent level statistical uncertainites are
typical for measurements at the Tevatron, and several mill level uncertainites
are typical at the LHC.Comment: Minor clarifications. Expression for r_{+-} corrected. 19 pages LaTex
+ Tables + 1 Figur
Optimized Variables of the Study of Polarization
The value of the -baryon polarization can be extracted from inclusive data
at LEP with better than 10\% precision based on current statistics. We present
a new variable by which to measure the polarization, which is the ratio of the
average electron energy to the average neutrino energy. This variable is both
sensitive to polarization and insensitive to fragmentation uncertainties.Comment: 10 pages (LaTeX), 2 figures, MIT-CTP-2270, CERN-PPE/94-0
Radiative Decay of Vector Quarkonium: Constraints on Glueballs and Light Gluinos
Given a resonance of known mass, width, and J^{PC}, we can determine its
gluonic branching fraction, b(R->gg), from data on its production in radiative
vector quarkonium decay, V -> gamma+R. For most resonances b(R->gg) is found to
be O(10%), consistent with being q-qbar states, but we find that both
pseudoscalars observed in the 1440 MeV region have b(R->gg) ~ 1/2 - 1, and
b(f_0^{++}->gg) ~ 1/2. As data improves, b(R->gg) should be a useful
discriminator between q-qbar and gluonic states and may permit quantitative
determination of the extent to which a particular resonance is a mixture of
glueball and q-qbar. We also examine the regime of validity of pQCD for
predicting the rate of V -> gamma+eta_gluino, the ``extra'' pseudoscalar bound
state which would exist if there were light gluinos. From the CUSB limit on
peaks in Upsilon -> gamma X, the mass range 3 GeV < m(eta_gluino) < 7 GeV can
be excluded. An experiment must be significantly more sensitive to exclude an
eta_gluino lighter than this.Comment: 36pp (inc figs),RU-94-04. (Replaces original which didn't latex
correctly and didn't have figures.
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