[Show abstract][Hide abstract] ABSTRACT: This work is on the Physics of the B Factories. Part A of this book contains
a brief description of the SLAC and KEK B Factories as well as their detectors,
BaBar and Belle, and data taking related issues. Part B discusses tools and
methods used by the experiments in order to obtain results. The results
themselves can be found in Part C.
European Physical Journal C 11/2014; DOI:10.1140/epjc/s10052-014-3026-9 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present an update of our determination of the strong coupling alpha(s) from the quantum chromodynamics static energy. This updated analysis includes new lattice data, at smaller lattice spacings and reaching shorter distances, the use of better suited perturbative expressions to compare with data in a wider distance range, and a comprehensive and detailed estimate of the error sources that contribute to the uncertainty of the final result. Our updated value for alpha(s) at the Z-mass scale, M-Z, is alpha(s)(M-Z) = 0.1166(-0.0008)(+0.0012), which supersedes our previous result.
Physical Review D 10/2014; 90(7). DOI:10.1103/PhysRevD.90.074038 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The complete expression of the heavy quark-antiquark potential up to order
$1/m^2$ is known from QCD in terms of Wilson loop expectation values. We use
that expression and a mapping, assumed to be valid at large distances, between
Wilson loop expectation values and correlators evaluated in the effective
string theory, to compute the potential. We obtain previously unknown results
for the spin and momentum-independent parts of the potential. They may be
interpreted as relativistic corrections to the string tension, $\sigma$,
effectively reducing it by an amount $9\,\zeta_3/(2\pi^3) \times (\sigma/m)^2$
in the equal mass case. We confirm known results for the other parts of the
potential. Finally, we compute the discrete spectrum of a heavy quark-antiquark
pair whose interaction is just given by the potential prescribed by the
effective string theory.
Physical Review D 07/2014; 90(11). DOI:10.1103/PhysRevD.90.114032 · 4.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We highlight the progress, current status, and open challenges of QCD-driven
physics, in theory and in experiment. We discuss how the strong interaction is
intimately connected to a broad sweep of physical problems, in settings ranging
from astrophysics and cosmology to strongly-coupled, complex systems in
particle and condensed-matter physics, as well as to searches for physics
beyond the Standard Model. We also discuss how success in describing the strong
interaction impacts other fields, and, in turn, how such subjects can impact
studies of the strong interaction. In the course of the work we offer a
perspective on the many research streams which flow into and out of QCD, as
well as a vision for future developments.
European Physical Journal C 04/2014; 74(10). DOI:10.1140/epjc/s10052-014-2981-5 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We give a short overview of the renormalization properties of rectangular
Wilson loops, the Polyakov loop correlator and the cyclic Wilson loop. We then
discuss how to renormalize loops with more than one intersection, using the
simplest non-trivial case as an illustrative example. Our findings expand on
previous treatments. The generalized exponentiation theorem is applied to the
Polyakov loop correlator and used to renormalize linear divergences in the
cyclic Wilson loop.
Physics of Particles and Nuclei 12/2013; 45(4). DOI:10.1134/S1063779614040029 · 0.62 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Heavy Majorana neutrinos enter in many scenarios of physics beyond the
Standard Model: in the original seesaw mechanism they provide a natural
explanation for the small masses of the Standard Model neutrinos and in the
simplest leptogenesis framework they are at the origin of the baryonic matter
of the universe. In this paper, we develop an effective field theory for
non-relativistic Majorana particles, which is analogous to the heavy-quark
effective theory. Then, we apply it to the case of a heavy Majorana neutrino
decaying in a hot and dense plasma of Standard Model particles, whose
temperature is much smaller than the mass of the Majorana neutrino but still
much larger than the electroweak scale. The thermal corrections to the width
computed in the effective field theory agree with recent results obtained using
different methods, whereas the derivation appears to be simpler. The effective
field theory presented here is suitable to be used for a variety of different
models involving non-relativistic Majorana fermions.
Journal of High Energy Physics 07/2013; 2013(12). DOI:10.1007/JHEP12(2013)028 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We study the symmetries of the three-heavy-quark system under exchange of the quark fields within the effective field theory framework of potential nonrelativistic QCD. The symmetries constrain the form of the matching coefficients in the effective theory. We then focus on the color-singlet sector and determine the so far unknown leading ultrasoft contribution to the static potential, which is of order αs4lnμ, and consequently to the static energy, which is of order αs4lnαs. Finally, in the case of an equilateral geometry, we solve the renormalization group equations and resum the leading ultrasoft logarithms for the static potential of three quarks in a color singlet, octet and decuplet representation.
[Show abstract][Hide abstract] ABSTRACT: In a weak-coupling effective field theory framework we study quarkonium
dissociation induced by inelastic scattering with partons in the medium. This
is the dominant dissociation process for temperatures such that the Debye mass
is larger than the binding energy. We evaluate the dissociation cross section
and the corresponding thermal decay width. At leading order we derive a
convolution formula relating the two, which is consistent with the optical
theorem and QCD at finite temperature. Bound state effects are systematically
included. They add contributions to the cross section and width that are beyond
a quasi-free approximation, whose validity is critically reviewed. For
temperatures such that the Debye mass is smaller than the binding energy, the
dominant dissociation mechanism is gluo-dissociation consisting in quarkonium
dissociation induced by the absorbtion of a gluon from the medium. We calculate
the gluo-dissociation cross section and width at next-to-leading-order
accuracy.
Journal of High Energy Physics 03/2013; 2013(5). DOI:10.1007/JHEP05(2013)130 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In finite-temperature field theory, the cyclic Wilson loop is defined as a
rectangular Wilson loop spanning the whole compactified time direction. In a
generic non-abelian gauge theory, we calculate the perturbative expansion of
the cyclic Wilson loop up to order g^4. At this order and after charge
renormalization, the cyclic Wilson loop is known to be ultraviolet divergent.
We show that the divergence is not associated with cusps in the contour but is
instead due to the contour intersecting itself because of the periodic boundary
conditions. One consequence of this is that the cyclic Wilson loop mixes under
renormalization with the correlator of two Polyakov loops. The resulting
renormalization equation is tested up to order g^6 and used to resum the
leading logarithms associated with the intersection divergence. Implications
for lattice studies of this operator, which may be relevant for the
phenomenology of quarkonium at finite temperature, are discussed.
Journal of High Energy Physics 12/2012; 2013(3). DOI:10.1007/JHEP03(2013)069 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the framework of Soft-Collinear Effective Theory, the jet quenching
parameter, $\hat{q}$, has been evaluated by adding the effect of Glauber gluon
interactions to the propagation of a highly-energetic collinear parton in a
medium. The result, which holds in covariant gauges, has been expressed in
terms of the expectation value of two Wilson lines stretching along the
direction of the four-momentum of the parton. In this paper, we show how that
expression can be generalized to an arbitrary gauge by the addition of
transverse Wilson lines. The transverse Wilson lines are explicitly computed by
resumming interactions of the parton with Glauber gluons that appear only in
non-covariant gauges. As an application of our result, we discuss the
contribution to $\hat{q}$ coming from transverse momenta of order $g^2T$ in a
medium that is a weakly-coupled quark-gluon plasma.
Journal of High Energy Physics 08/2012; 2013(2). DOI:10.1007/JHEP02(2013)129 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We compare lattice data for the short-distance part of the static energy in
2+1 flavor quantum chromodynamics (QCD) with perturbative calculations, up to
next-to-next-to-next-to leading-logarithmic accuracy. We show that perturbation
theory describes very well the lattice data at short distances, and exploit
this fact to obtain a determination of the product of the lattice scale r_0
with the QCD scale Lambda_{MS}. With the input of the value of r_0, this
provides a determination of the strong coupling alpha_s at the typical distance
scale of the lattice data. We obtain alpha_s(1.5 GeV)=0.326\pm0.019, which
provides a novel determination of alpha_s at low energy and with three-loop
accuracy (including resummation of the leading ultrasoft logarithms). When this
value is evolved to the Z-mass scale M_Z, it corresponds to
alpha_s(M_Z)=0.1156^{+0.0021}_{-0.0022}.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: These are the proceedings of the "Workshop on Precision Measurements of
alphas" held at the Max-Planck-Institute for Physics, Munich, February 9-11,
2011. The workshop explored in depth the determination of alphas(mZ) in the
MS-bar scheme from the key categories where high precision measurements are
currently being made, including DIS and global PDF fits, tau-decays,
electroweak precision observables and Z-decays, event-shapes, and lattice QCD.
These proceedings contain a short summary contribution from the speakers, as
well as the lists of authors, conveners, participants, and talks.
[Show abstract][Hide abstract] ABSTRACT: The thermal width of heavy-quarkonium bound states in a quark-gluon plasma
has been recently derived in an effective field theory approach. Two phenomena
contribute to the width: the Landau damping phenomenon and the break-up of a
colour-singlet bound state into a colour-octet heavy quark-antiquark pair by
absorption of a thermal gluon. In the paper, we investigate the relation
between the singlet-to-octet thermal break-up and the so-called
gluo-dissociation, a mechanism for quarkonium dissociation widely used in
phenomenological approaches. The gluo-dissociation thermal width is obtained by
convoluting the gluon thermal distribution with the cross section of a gluon
and a 1S quarkonium state to a colour octet quark-antiquark state in vacuum, a
cross section that at leading order, but neglecting colour-octet effects, was
computed long ago by Bhanot and Peskin. We will, first, show that the effective
field theory framework provides a natural derivation of the gluo-dissociation
factorization formula at leading order, which is, indeed, the singlet-to-octet
thermal break-up expression. Second, the singlet-to-octet thermal break-up
expression will allow us to improve the Bhanot--Peskin cross section by
including the contribution of the octet potential, which amounts to include
final-state interactions between the heavy quark and antiquark. Finally, we
will quantify the effects due to final-state interactions on the
gluo-dissociation cross section and on the quarkonium thermal width.
Journal of High Energy Physics 09/2011; 2011(12). DOI:10.1007/JHEP12(2011)116 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Heavy quarkonium at finite temperature has been the subject of intense theoretical studies, for it provides a potentially
clean probe of the quark-gluon plasma. Recent studies have made use of effective field theories to exploit in a systematic
manner the hierarchy of energy scales that characterize the system. In the case of a quarkonium in a medium whose temperature
is smaller than the typical momentum transfer in the bound state but larger than its energy, the suitable effective field
theory is pNRQCDHTL, where degrees of freedom with energy or momentum larger than the binding energy have been integrated out. Thermal effects
are expected to break Poincaré invariance, which, at zero temperature, manifests itself in a set of exact relations between
the matching coefficients of the effective field theory. In the paper, we evaluate the leading-order thermal corrections to
the spin-orbit potentials of pNRQCDHTL and show that Poincaré invariance is indeed violated.
KeywordsHeavy Quark Physics–Thermal Field Theory–QCD
Journal of High Energy Physics 07/2011; 2011(7):1-18. DOI:10.1007/JHEP07(2011)096 · 6.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: I review some recent progress, open puzzles and future opportunities in heavy
quarkonium physics in the framework of effective field theories
[Show abstract][Hide abstract] ABSTRACT: We present an effective field theory based extraction of the
ɛc mass and width from a recent measurement by CLEO
of the photon line shape in the
J/ψ-->ɛcγ decay.
[Show abstract][Hide abstract] ABSTRACT: We compute the complete imaginary part of the NRQCD Lagrangian at order 1/M^4
in the heavy-quark mass expansion, which includes center of mass operators, and
at order alpha_s^2 in the matching coefficients. We also compute the imaginary
part of the NRQCD Lagrangian at order 1/M^6 and at order alpha_s^2 that
contributes to the S-wave and P-wave inclusive decay widths of heavy quarkonium
into light hadrons at order v^7 in the heavy-quark velocity expansion. If we
count alpha_s(M) ~ v^2, the calculation provides the complete next-to-leading
order corrections to the P-wave hadronic widths, and in the original NRQCD
power counting, the complete next-to-leading order corrections to the vector
S-wave widths, and part of the next-to-next-to leading order corrections to the
pseudoscalar S-wave widths. In the S-wave case, we confirm previous findings
and add new terms in a more conservative power counting. In the P-wave case,
our results are in disagreement with previous ones. Constraints induced by
Poincare' invariance on the NRQCD four-fermion sector are studied for the first
time and provide an additional check of the calculation. Perspectives for
phenomenological applications are discussed.