2,558 research outputs found
Interpreting experimental bounds on D^0 - \bar{D^0} mixing in the presence of CP violation
We analyse the most recent experimental data regarding D^0 - \bar{D^0}
mixing, allowing for CP violation. We focus on the dispersive part of the
mixing amplitude, M^D_{12}, which is sensitive to new physics contributions. We
obtain a constraint on the mixing amplitude: |M^D_{12}| < 6.2\times 10^{-11}
MeV at 95% C.L. . This constraint is weaker by a factor of about three than the
one which is obtained when no CP violation is assumed.Comment: 9 pages, revtex4; One reference updated, one reference added,
footnote 3 correcte
Beta cell function after weight loss: a clinical trial comparing gastric bypass surgery and intensive lifestyle intervention
The effects of various weight loss strategies on pancreatic beta cell function remain unclear. We aimed to compare the effect of intensive lifestyle intervention (ILI) and Roux-en-Y gastric bypass surgery (RYGB) on beta cell function. Design One year controlled clinical trial (ClinicalTrials.gov identifier NCT00273104). One hundred and nineteen morbidly obese participants without known diabetes from the MOBIL study (mean (s.d.) age 43.6 (10.8) years, body mass index (BMI) 45.5 (5.6) kg/m2, 84 women) were allocated to RYGB (n=64) or ILI (n=55). The patients underwent repeated oral glucose tolerance tests (OGTTs) and were categorised as having either normal (NGT) or abnormal glucose tolerance (AGT). Twenty-nine normal-weight subjects with NGT (age 42.6 (8.7) years, BMI 22.6 (1.5) kg/m2, 19 women) served as controls. OGTT-based indices of beta cell function were calculated. One year weight reduction was 30 % (8) after RYGB and 9 % (10) after ILI (P<0.001). Disposition index (DI) increased in all treatment groups (all P<0.05), although more in the surgery groups (both P<0.001). Stimulated proinsulin-to-insulin (PI/I) ratio decreased in both surgery groups (both P<0.001), but to a greater extent in the surgery group with AGT at baseline (P<0.001). Post surgery, patients with NGT at baseline had higher DI and lower stimulated PI/I ratio than controls (both P<0.027). Gastric bypass surgery improved beta cell function to a significantly greater extent than ILI. Supra-physiological insulin secretion and proinsulin processing may indicate excessive beta cell function after gastric bypass surgery
Matter effects in the D0-D0bar system
We discuss the impact of matter effects in the D0-D0bar system. We show that
such effects could, in principle, be measured, but that they cannot be used to
probe the mass difference x_D or the lifetime difference y_D. This occurs
because the mixing effects and the matter effects decouple at short times. We
also comment briefly on the B systems.Comment: 6 pages, RevTe
Photon-Photon and Photon-Hadron Interactions at Relativistic Heavy Ion Colliders
In central collisions at relativistic heavy ion colliders like the
Relativistic Heavy Ion Collider RHIC/Brookhaven and the Large Hadron Collider
LHC (in its heavy ion mode) at CERN/Geneva, one aims at detecting a new form of
hadronic matter --- the Quark Gluon Plasma. We discuss here a complementary
aspect of these collisions, the very peripheral ones. Due to coherence, there
are strong electromagnetic fields of short duration in such collisions. They
give rise to photon-photon and photon-nucleus collisions with high flux up to
an invariant mass region hitherto unexplored experimentally. After a general
survey photon-photon luminosities in relativistic heavy ion collisions are
discussed. Then photon-photon physics at various gamma-gamma-invariant mass
scales is discussed. The region of several GeV, relevant for RHIC is dominated
by QCD phenomena (meson and vector meson pair production). Invariant masses of
up to about 100 GeV can be reached at LHC, and the potential for new physics is
discussed. Lepton-pair production, especially electron-positron pair production
is copious. Due to the strong fields there will be new phenomena, especially
multiple e+e- pair production.Comment: 10 pages, Proceedings of the Erice Summer School on Heavy Ion Physics
199
Phenomenological Consequences of Right-handed Down Squark Mixings
The mixings of quarks, hidden from view in Standard Model (SM), are
naturally the largest if one has an Abelian flavor symmetry. With supersymmetry
(SUSY) their effects can surface via squark loops. Squark and
gluino masses are at TeV scale, but they can still induce effects comparable to
SM in (or ) mixings, while mixing could be close to recent
hints from data. In general, CP phases would be different from SM, as may be
indicated by recent B Factory data. Presence of non-standard soft SUSY
breakings with large could enhance (or )
transitions.Comment: Version to appear in Phys. Rev. Let
Determining using with multibody D decays
We propose a method for determining using decays
followed by a multibody decay, such as , and . The main advantages of the method is
that it uses only Cabibbo allowed decays, and that large strong phases are
expected due to the presence of resonances. Since no knowledge about the
resonance structure is needed, can be extracted without any hadronic
uncertainty.Comment: 17 pages, 1 figur
Tau and Charm physics highlights
In tau physics, we are at the frontier between the completion of the LEP
program and the start of analyses from b-factories, which are expected to
produce results in the coming years. Nice results from CLEO are steadily
delivered in the meantime. For charm, impressive progress have been achieved by
fixed target experiments in the search for CP violation and D^0 - \bar D^0
oscillations. First results from b-factories demonstrate the power of these
facilities in such areas. The novel measurement of the D* width by CLEO happens
to be rather different from current expectations. The absence of a charm
factory explains the lack or the very slow progress in the absolute scale
determinations for charm decays.Comment: "Typos corrected and references added
Averages of b-hadron Properties at the End of 2005
This article reports world averages for measurements on b-hadron properties
obtained by the Heavy Flavor Averaging Group (HFAG) using the available results
as of at the end of 2005. In the averaging, the input parameters used in the
various analyses are adjusted (rescaled) to common values, and all known
correlations are taken into account. The averages include lifetimes, neutral
meson mixing parameters, parameters of semileptonic decays, branching fractions
of B meson decays to final states with open charm, charmonium and no charm, and
measurements related to CP asymmetries
Implications of Recent Measurements of Hadronic Charmless B Decays
Implications of recent CLEO measurements of hadronic charmless B decays are
discussed. (i) Employing the Bauer-Stech-Wirbel (BSW) model for form factors as
a benchmark, the data indicate that the form factor
is smaller than that predicted by the BSW model, whereas the
data of imply that the form factors are greater than the BSW model's values. (ii) The tree-dominated
modes imply that the effective
number of colors N_c(LL) for (V-A)(V-A) operators is preferred to be smaller,
while the current limit on shows that N_c(LR)>3. The data of and clearly indicate that . (iii) In
order to understand the observed suppression of and
non-suppression of modes, both being governed by the form factor
, the unitarity angle is preferred to be greater than
. By contrast, the new measurement of no
longer strongly favors . (iv) The observed pattern K^-\pi^+\sim
\ov K^0\pi^-\sim {2\over 3}K^-\pi^0 is consistent with the theoretical
expectation: The constructive interference between electroweak and QCD penguin
diagrams in the mode explains why {\cal B}(B^-\to K^-\pi^0)>{1\over
2}{\cal B}(\ov B^0\to K^-\pi^+). (v) The observation \nc(LL)<3<\nc(LR) and
our preference for \nc(LL)\sim 2 and \nc(LR)\sim 6 are justified by a
recent perturbative QCD calculation of hadronic rare B decays in the heavy
quark limit.Comment: 21 pages; CLEO measurements of several charmless B decay modes are
updated. Discussion of the unitarity angle gamma in the \rho\pi mode is
revise
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