2,977 research outputs found
The 1P quarkonium fine splittings at NLO
We calculate the 1P heavy quarkonium fine splittings at NLO and discuss the
impact of the calculation on the chi_b(1P) splittings.Comment: 10 pages, 3 figure
Effective Field Theories for Heavy Quarkonium
We briefly review how nonrelativistic effective field theories give us a
definition of the QCD potentials and a coherent field theory derived quantum
mechanical scheme to calculate the properties of bound states made by two or
more heavy quarks. In this framework heavy quarkonium properties depend only on
the QCD parameters (quark masses and \als) and nonpotential corrections are
systematically accounted for. The relation between the form of the
nonperturbative potentials and the low energy QCD dynamics is also discussed.Comment: Invited Plenary talk at The 20th European Conference on Few-Body
Problems in Physics. September 10-14 2007. Pisa, Italy. To be published on
Few-Body System
Overview of charmonium decays and production from Non-Relativistic QCD
I briefly review Non-Relativistic QCD and related effective theories, and
discuss applications to heavy quarkonium decay, and production in
electron-positron colliders.Comment: 8 pages, Invited talk at Charm 2010, Oct. 21-24, IHEP, Beijin
Heavy Quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature
We calculate the heavy quarkonium energy levels and decay widths in a
quark-gluon plasma, whose temperature T and screening mass m_D satisfy the
hierarchy m alpha_s >> T >> m alpha_s^2 >> m_D (m being the heavy-quark mass),
at order m alpha_s^5. We first sequentially integrate out the scales m, m
alpha_s and T, and, next, we carry out the calculations in the resulting
effective theory using techniques of integration by regions. A collinear region
is identified, which contributes at this order. We also discuss the
implications of our results concerning heavy quarkonium suppression in heavy
ion collisions.Comment: 25 pages, 2 figure
The QCD Potential at
Within an effective field theory framework, we obtain an expression for the
next-to-leading term in the expansion of the singlet QCD
potential in terms of Wilson loops, which holds beyond perturbation theory. The
ambiguities in the definition of the QCD potential beyond leading order in
are discussed and a specific expression for the potential is given.
We explicitly evaluate this expression at one loop and compare the outcome with
the existing perturbative results. On general grounds we show that for quenched
QED and fully Abelian-like models this expression exactly vanishes.Comment: 19 pages, LaTeX, 1 figure. Journal version. Discussion refined,
misprints corrected, few references added; results unchange
Model-independent Study of Electric Dipole Transitions in Quarkonium
The paper contains a systematic, model-independent treatment of electric
dipole (E1) transitions in heavy quarkonium. Within the effective field theory
framework of potential non-relativistic QCD (pNRQCD), we derive the complete
set of relativistic corrections of relative order v^2 both for weakly and
strongly-coupled quarkonia. The result supports and complements former results
from potential model calculations.Comment: 42 pages, 9 figure
Top Threshold Physics
Running a future Linear Collider at the top pair threshold allows for precise
measurements of the mass, the widths and the couplings of the top quark. I give
a nontechnical review on recent theoretical developments and the theory status
in top threshold physics concerning QCD corrections and top quark finite
lifetime and electroweak effects. I also discuss threshold physics in the
context of measurements of the top Yukawa coupling from
and of squark pair production.Comment: 13 pages, 6 figures, PoS style. Invited talk presented at the
International Workshop on Top Quark Physics, Coimbra, Portugal, 12-15 Jan
200
On the dimensions of secant varieties of Segre-Veronese varieties
This paper explores the dimensions of higher secant varieties to
Segre-Veronese varieties. The main goal of this paper is to introduce two
different inductive techniques. These techniques enable one to reduce the
computation of the dimension of the secant variety in a high dimensional case
to the computation of the dimensions of secant varieties in low dimensional
cases. As an application of these inductive approaches, we will prove
non-defectivity of secant varieties of certain two-factor Segre-Veronese
varieties. We also use these methods to give a complete classification of
defective s-th Segre-Veronese varieties for small s. In the final section, we
propose a conjecture about defective two-factor Segre-Veronese varieties.Comment: Revised version. To appear in Annali di Matematica Pura e Applicat
From the Feynman-Schwinger representation to the non-perturbative relativistic bound state interaction
We write the 4-point Green function in QCD in the Feynman-Schwinger
representation and show that all the dynamical information are contained in the
Wilson loop average. We work out the QED case in order to obtain the usual
Bethe-Salpeter kernel. Finally we discuss the QCD case in the non-perturbative
regime giving some insight in the nature of the interaction kernel.Comment: 25 pages, RevTex, 3 figures included, typos corrected, to appear in
Phys. Rev. D 5
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