3,002 research outputs found
Dipenguin-like contributions to D0 - anti-D0 mixing
We show that because of the milder GIM suppression, the four-quark dipenguin
operator contributes to the short distance piece of the D^0-\bar D^0 mixing
amplitude at the same order of magnitude as the box diagram. In addition, we
put an upper bound \Delta m_D^{LDR} \leq 5 \times \Delta m_D^{box} on a
long-distance resonant contribution induced by the penguin mixing.Comment: 4 pages, 1 figure; to appear in the proceedings of HADRON'97, BNL,
August 1997; preprint number is adde
CP-violation and mixing in charmed mesons
The Standard Model contribution to D0-anti-D0 mixing is dominated by the
contributions of light s and d quarks. Neglecting the tiny effects due to b
quark, both mass and lifetime differences vanish in the limit of SU(3)_F
symmetry. Thus, the main challenge in the Standard Model calculation of the
mass and width difference in the D0-anti-D0 system is to estimate the size of
SU(3) breaking effects. We prove that D meson mixing occurs in the Standard
Model only at second order in SU(3) violation. We consider the possibility that
phase space effects may be the dominant source of SU(3) breaking. We find that
y=(\Delta \Gamma)/(2\Gamma) of the order of one percent is natural in the
Standard Model, potentially reducing the sensitivity to new physics of
measurements of D meson mixing. We also discuss the possibility of observing
lifetime differences and CP violation in charmed mesons both at the currently
operating and proposed facilities.Comment: 13 pages, no figures, invited talk at Continuous Advances in QCD 2002
/ ARKADYFEST, May 17-23, 200
X(3872) in effective field theory
We consider the implications from the possibility that the recently observed
state X(3872) is a meson-antimeson molecule. We write an effective Lagrangian
consistent with the heavy-quark and chiral symmetries needed to describe
X(3872) and study its properties.Comment: 4 pages, presented at Particles and Nuclei International Conference
(PANIC 05), Santa Fe, New Mexico, 24-28 Oct 200
The use of neutrino beams from muon storage rings
I give a brief overview of the physics potential of short baseline
experiments at neutrino factories, i.e. facilities providing high energy and
high intensity neutrino beams, like the one planned to be built in connection
with the proposed high energy muon storage ring. These facilities would offer a
unique opportunity to perform new precision studies of QCD and electroweak
interactions. New types of measurements, such as studies of gluon density of
the nucleon via charmonium production and extractions of V_cb and V_ub CKM
matrix elements, will become possible. Interesting new physics scenarios can
also be explored.Comment: 8 pages, no figures, based on invited talks given at 23rd Johns
Hopkins Workshop on Current Problems in Particle Theory: Neutrinos in the
Next Millennium, Baltimore, MD, 10-12 June 1999, and The International
Conference on Physics Potential and Development of mu+ mu- Colliders, San
Francisco, CA, 15-17 December 199
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