81 research outputs found
Progress in multiloop calculations
I briefly summarize the talks on calculation of multiloop Feynman diagrams
presented at ACAT'2002 (Moscow University).Comment: Section summary talk at ACAT'2002 (Moscow
HQET chromomagnetic interaction at two loops
We present the coefficient of the chromomagnetic interaction operator, the
only unknown coefficient in the Heavy Quark Effective Theory (HQET) lagrangian
up to the level, with the two-loop accuracy by matching scattering
amplitudes of an on-shell heavy quark in an external field in full QCD and
HQET, and obtain the two-loop anomalous dimension of this operator in HQET.Comment: 10 pages, LaTeX2e, 2 eps figures included. Revised discussion of
(n_f-1)-flavour HQET include
Three-Loop Chromomagnetic Interaction in HQET
We compute the three-loop QCD corrections to the quark chromomagnetic moment
and thus obtain the matching coefficient and the anomalous dimension of the
chromomagnetic interaction in HQET. As a byproduct we obtain the three-loop
corrections to the quark anomalous magnetic moment.Comment: 22 page
First hint of non-standard CP violation from B --> Phi K_S decay
We comment on the implications of the recently measured CP asymmetry in B -->
Phi K_S decay. The data disfavor the Standard Model at 2.7 sigma and -if the
trend persists in the future with higher statistics - require the existence of
CP violation beyond that in the CKM matrix. In particular, the b --> s bar{s} s
decay amplitude would require new contributions of comparable size to the
Standard Model ones with an order one phase. While not every model can deliver
such a large amount of CP and flavor violation, those with substantial FCNC
couplings to the Z can reproduce the experimental findings.Comment: references added and minor text changes; conclusions unchanged; PRD
version; 5 pages, 2 figures, uses espcrc2.st
and in the Standard Model and new bounds on R parity violation
We study the pure penguin decays and .
Using QCD factorization, we find . For the pure penguin annihilation process
, analyzed here for the first time, . The smallness of these decays in
the Standard Model makes them sensitive probes for new physics. From the upper
limit of ,we find constraints on R parity violating couplings, , and for . Our new bounds on
are one order of magnitude stronger than
before. Within the available upper bounds for , and
, we find that could
be enhanced to . Experimental searches for these decays
are strongly urged.Comment: 5 pages, 3 figures embede
B --> Phi K_S and Supersymmetry
The rare decay B --> Phi K_S is a well-known probe of physics beyond the
Standard Model because it arises only through loop effects yet has the same
time-dependent CP asymmetry as B --> Psi K_S. Motivated by recent data
suggesting new physics in B --> Phi K_S, we look to supersymmetry for possible
explanations, including contributions mediated by gluino loops and by Higgs
bosons. Chirality-preserving LL and RR gluino contributions are generically
small, unless gluinos and squarks masses are close to the current lower bounds.
Higgs contributions are also too small to explain a large asymmetry if we
impose the current upper limit on B(B_s --> mu mu). On the other hand,
chirality-flipping LR and RL gluino contributions can provide sizable effects
and while remaining consistent with related results in B --> Psi K_S, Delta
M_s, B --> X_s gamma and other processes. We discuss how the LR and RL
insertions can be distinguished using other observables, and we provide a
string-based model and other estimates to show that the needed sizes of mass
insertions are reasonable.Comment: 33 pages, 32 figures, Updated version for PRD. Includes discussions
of other recent works on this topic. Added discussions & plots for gluino
mass dependence and effects of theoretical uncertaintie
Alterations to nuclear architecture and genome behavior in senescent cells.
The organization of the genome within interphase nuclei, and how it interacts with nuclear structures is important for the regulation of nuclear functions. Many of the studies researching the importance of genome organization and nuclear structure are performed in young, proliferating, and often transformed cells. These studies do not reveal anything about the nucleus or genome in nonproliferating cells, which may be relevant for the regulation of both proliferation and replicative senescence. Here, we provide an overview of what is known about the genome and nuclear structure in senescent cells. We review the evidence that nuclear structures, such as the nuclear lamina, nucleoli, the nuclear matrix, nuclear bodies (such as promyelocytic leukemia bodies), and nuclear morphology all become altered within growth-arrested or senescent cells. Specific alterations to the genome in senescent cells, as compared to young proliferating cells, are described, including aneuploidy, chromatin modifications, chromosome positioning, relocation of heterochromatin, and changes to telomeres
Exploring flavor structure of supersymmetry breaking from rare B decays and unitarity triangle
We study effects of supersymmetric particles in various rare B decay
processes as well as in the unitarity triangle analysis. We consider three
different supersymmetric models, the minimal supergravity, SU(5) SUSY GUT with
right-handed neutrinos, and the minimal supersymmetric standard model with U(2)
flavor symmetry. In the SU(5) SUSY GUT with right-handed neutrinos, we consider
two cases of the mass matrix of the right-handed neutrinos. We calculate direct
and mixing-induced CP asymmetries in the b to s gamma decay and CP asymmetry in
B_d to phi K_S as well as the B_s--anti-B_s mixing amplitude for the unitarity
triangle analysis in these models. We show that large deviations are possible
for the SU(5) SUSY GUT and the U(2) model. The pattern and correlations of
deviations from the standard model will be useful to discriminate the different
SUSY models in future B experiments.Comment: revtex4, 36 pages, 10 figure
B decays and models for CP violation
The decay modes to , , , and
are promising channels to study the unitarity triangle of the CP violating CKM
matrix. In this paper I study the consequences of these measurements in the
Weinberg model. I show that using the same set of measurements, the following
different mechanisms for CP violation can be distinguished: 1) CP is violated
in the CKM sector only; 2) CP is violated spontaneously in the Higgs sector
only; And 3) CP is violated in both the CKM and Higgs sectors.Comment: 18 pagers, Revtex, Four compressed figures. Some typos in the figure
captions are correcte
ATP synthase: from single molecule to human bioenergetics
ATP synthase (FoF1) consists of an ATP-driven motor (F1) and a H+-driven motor (Fo), which rotate in opposite directions. FoF1 reconstituted into a lipid membrane is capable of ATP synthesis driven by H+ flux. As the basic structures of F1 (α3β3γδε) and Fo (ab2c10) are ubiquitous, stable thermophilic FoF1 (TFoF1) has been used to elucidate molecular mechanisms, while human F1Fo (HF1Fo) has been used to study biomedical significance. Among F1s, only thermophilic F1 (TF1) can be analyzed simultaneously by reconstitution, crystallography, mutagenesis and nanotechnology for torque-driven ATP synthesis using elastic coupling mechanisms. In contrast to the single operon of TFoF1, HFoF1 is encoded by both nuclear DNA with introns and mitochondrial DNA. The regulatory mechanism, tissue specificity and physiopathology of HFoF1 were elucidated by proteomics, RNA interference, cytoplasts and transgenic mice. The ATP synthesized daily by HFoF1 is in the order of tens of kilograms, and is primarily controlled by the brain in response to fluctuations in activity
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