Publications (142)
 [Show abstract] [Hide abstract] ABSTRACT: We study the free energy of a static quark in QCD with 2+1 flavors in a wide temperature region, 116 MeV $< T < $ 5814 MeV, using the highly improved staggered quark (HISQ) action. We analyze the transition region in detail, obtain the entropy of a static quark, show that it peaks at temperatures close to the chiral crossover temperature and also revisit the temperature dependence of the Polyakov loop susceptibilities using gradient flow. We discuss the implications of our findings for the deconfinement and chiral crossover phenomena at physical values of the quark masses. Finally a comparison of the lattice results at high temperatures with the weakcoupling calculations is presented.
 [Show abstract] [Hide abstract] ABSTRACT: We calculate the nexttonexttoleading correction to the expectation value of the Polyakov loop or equivalently to the free energy of a static charge. This correction is of order $g^5$. We show that up to this order the free energy of the static charge is proportional to the quadratic Casimir operator of the corresponding representation. We also compare our perturbative result with the most recent lattice results in SU(3) gauge theory.

Article: Studies of Hadron Structure and Interactions with the $\overline{{\bf P}}$ANDA Experiment at FAIR
[Show abstract] [Hide abstract] ABSTRACT: The $\overline{\mbox{P}}$ANDA experiment together with the high quality antiproton beam at HESR will be a powerful tool to address fundamental questions of hadron physics in the charm and multistrange hadron sector. In connection with the recent data in the hidden charm sector, $\overline{\mbox{P}}$ANDA will be able to deliver decisive contributions to this field, due to the complementarity of the $\overline{p} p$ entrance channel and the capabilities of the combined storage ring and detector system under construction. 
Article: Resonances in QCD
[Show abstract] [Hide abstract] ABSTRACT: We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 1214, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with ${\it up}$, ${\it down}$ and ${\it strange}$ quark content were considered. For heavylight and heavyheavy meson systems, those with ${\it charm}$ quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here. 
Article: CP asymmetry in heavy Majorana neutrino decays at finite temperature: the nearly degenerate case
[Show abstract] [Hide abstract] ABSTRACT: In a model where Majorana neutrinos heavier than the electroweak scale couple to Standard Model Higgs bosons and leptons, we compute systematically thermal corrections to the direct and indirect CP asymmetries in the Majorana neutrino decays. These are key ingredients entering the equations that describe the thermodynamic evolution of the induced leptonnumber asymmetry eventually leading to the baryon asymmetry in the universe. We compute the thermal corrections in an effective field theory framework that assumes the temperature smaller than the masses of the Majorana neutrinos and larger than the electroweak scale, and we provide the leading corrections in an expansion of the temperature over the mass. In this work, we consider the case of two Majorana neutrinos with nearly degenerate masses.  [Show abstract] [Hide abstract] ABSTRACT: We derive an analytical expression for the chromopolarizability of $1S$bottomonium states using weaklycoupled pNRQCD. In this setting the intermediate octet states have Coulombic continuum wavefunctions. We use the QCD trace anomaly to obtain the twopion production amplitude for the chromopolarizability operator and match the result to a Chiral Effective Field Theory (EFT) with $1S$bottomonium states and pions as degreesoffreedom. In this chiral EFT we compute long range properties of the $1S$bottomonium generated by the pion coupling such as the leading chiral log to the $1S$bottomonium mass and the van der Waals potential between two $1S$bottomonium states.
 [Show abstract] [Hide abstract] ABSTRACT: We construct a nonrelativistic effective field theory description of heavy quarkonium hybrids from QCD. We identify the symmetries of the system made of a heavy quark, a heavy antiquark, and glue in the static limit. Corrections to this limit can be obtained order by order in an expansion in the inverse of the mass $m$ of the heavy quark. At order $1/m$ in the expansion, we obtain at the level of potential NonRelativistic QCD a system of coupled Schr\"odinger equations that describes hybrid spinsymmetry multiplets, including the mixing of different static energies into the hybrid states, an effect known as $\Lambda$doubling in molecular physics. In the short distance, the static potentials depend on two nonperturbative parameters, the gluelump mass and the quadratic slope, which can be determined from lattice calculations. We adopt a renormalon subtraction scheme for the calculation of the perturbative part of the potential. We numerically solve the coupled Schr\"odinger equations and obtain the masses for the lowest lying spinsymmetry multiplets for $c\bar{c}$, $b\bar{c}$, and $b\bar{b}$ hybrids. The $\Lambda$doubling effect breaks the degeneracy between opposite parity spinsymmetry multiplets and lowers the mass of the multiplets that get mixed contributions of different static energies. We compare our findings to the experimental data, direct lattice computations, sum rules calculations, and discuss the relation to the BornOppenheimer approximation.

Article: Resonances in QCD

Article: The Physics of the B Factories
[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. Please note that version 3 on the archive is the auxiliary version of the Physics of the B Factories book. This uses the notation alpha, beta, gamma for the angles of the Unitarity Triangle. The nominal version uses the notation phi_1, phi_2 and phi_3. Please cite this work as Eur. Phys. J. C74 (2014) 3026.  [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 Zmass scale, MZ, is alpha(s)(MZ) = 0.1166(0.0008)(+0.0012), which supersedes our previous result.

Article: Effective string theory and the longrange relativistic corrections to the quarkantiquark potential
[Show abstract] [Hide abstract] ABSTRACT: The complete expression of the heavy quarkantiquark 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 momentumindependent 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 quarkantiquark pair whose interaction is just given by the potential prescribed by the effective string theory.  [Show abstract] [Hide abstract] ABSTRACT: We highlight the progress, current status, and open challenges of QCDdriven 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 stronglycoupled, complex systems in particle and condensedmatter 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.
 [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 nontrivial 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.
 [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 nonrelativistic Majorana particles, which is analogous to the heavyquark 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 nonrelativistic Majorana fermions.
 [Show abstract] [Hide abstract] ABSTRACT: We study the symmetries of the threeheavyquark 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 colorsinglet 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 weakcoupling 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 quasifree approximation, whose validity is critically reviewed. For temperatures such that the Debye mass is smaller than the binding energy, the dominant dissociation mechanism is gluodissociation consisting in quarkonium dissociation induced by the absorbtion of a gluon from the medium. We calculate the gluodissociation cross section and width at nexttoleadingorder accuracy.
 [Show abstract] [Hide abstract] ABSTRACT: In finitetemperature field theory, the cyclic Wilson loop is defined as a rectangular Wilson loop spanning the whole compactified time direction. In a generic nonabelian 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.
 [Show abstract] [Hide abstract] ABSTRACT: In the framework of SoftCollinear Effective Theory, the jet quenching parameter, $\hat{q}$, has been evaluated by adding the effect of Glauber gluon interactions to the propagation of a highlyenergetic 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 fourmomentum 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 noncovariant 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 weaklycoupled quarkgluon plasma.

 [Show abstract] [Hide abstract] ABSTRACT: We compare lattice data for the shortdistance part of the static energy in 2+1 flavor quantum chromodynamics (QCD) with perturbative calculations, up to nexttonexttonextto leadinglogarithmic 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 threeloop accuracy (including resummation of the leading ultrasoft logarithms). When this value is evolved to the Zmass scale M_Z, it corresponds to alpha_s(M_Z)=0.1156^{+0.0021}_{0.0022}.
Publication Stats
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Institutions

20092013

University of Technology Munich
 Faculty of Physics
München, Bavaria, Germany


20012011

University of Milan
 Department of Physics
Milano, Lombardy, Italy


19902011

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy


19962002

Azienda Sanitaria Locale di Milano
Milano, Lombardy, Italy


1999

University of Barcelona
 Department of Structure and Constituents of Matter
Barcino, Catalonia, Spain


1998

Heidelberg University
 Institute of Theoretical Physics
Heidelberg, BadenWuerttemberg, Germany
