We present the finite temperature spectra of both bottomonium and charmonium, obtained from a consistent lattice QCD based potential picture. Starting point is the complex in-medium potential extracted on full QCD lattices with dynamical u,d and s quarks, generated by the HotQCD collaboration. Using the generalized Gauss law approach, vetted in a previous study on quenched QCD, we fit ${\rm Re}[V]$ with a single temperature dependent parameter $m_D$, the Debye screening mass, and confirm the up to now tentative values of ${\rm Im}[V]$. The obtained analytic expression for the complex potential allows us to compute quarkonium spectral functions by solving an appropriate Schrödinger equation. These spectra exhibit thermal widths, which are free from the resolution artifacts that plague direct reconstructions from Euclidean correlators using Bayesian methods. In the present adiabatic setting, we find clear evidence for sequential melting and derive melting temperatures for the different bound states. Quarkonium is gradually weakened by both screening (${\rm Re}[V]$) and scattering (${\rm Im}[V]$) effects that in combination lead to a shift of their in-medium spectral features to smaller frequencies, contrary to the mass gain of elementary particles at finite temperature.
We present a phenomenological study of the $x_F$ dependence of quarkonium production in high energy proton-nucleus collisions. The \xf~dependence of comover contributions is introduced to account for the observed quarkonium suppression at low $x_F$. Combining comover contributions, nuclear shadowing effect, energy loss mechanism and nuclear absorption together we reproduce the overall \xf~dependence of E772/E789 data.
We present an improved analytic parametrisation of the complex in-medium heavy quark potential derived rigorously from the generalised Gauss law. To this end we combine in a self-consistent manner a non-perturbative vacuum potential with a weak-coupling description of the QCD medium. The resulting Gauss-law parametrisation is able to reproduce full lattice QCD data by using only a single temperature dependent parameter, the Debye mass $m_D$. Using this parametrisation we model the in-medium potential at finite baryo-chemical potential, which allows us to estimate the $Ψ^\prime$/$J/Ψ$ ratio in …
Broad meson phenomenology in vacuum is discussed in a single model containing scalar, pseudoscalar, vector and axial-vector states both in the non-strange and strange sectors. Emphasis is given to search for quark-antiquark (quarkonium) states in the scalar and axial-vector channels. In particular, the work examines the question whether the scalar quark-antiquark states are found in the energy region below or above 1 GeV in the physical spectrum. Contrarily to the naive expectation, the mentioned states are found in the region above 1 GeV. Additionally, the axial-vector isotriplet state $a_1(1…
In the framework of a specific scheme of the QCD sum rules for $S$-wave levels of the heavy quarkonium, one derives expressions, relating the leptonic constants, the energetic density of quarkonium states and universal characteristics in the heavy quarkonium physics, such as the difference between the masses of heavy quark $Q$ and meson $(Q\bar q)$ and the number of heavy quarkonium levels below the threshold of $(Q\bar Q) \to (Q\bar q) + (\bar Q q)$ decay.
We review recent developments in heavy-quarkonium phenomenology within the nonrelativistic QCD factorization approach. Main issues we consider in this work include the polarization of prompt J/psi at the Fermilab Tevatron and the large relativistic and QCD corrections to double-charmonium production at the B factories. We also consider inclusive charm production in bottomonia decays.
Using the open quantum system formalism and effective field theory of QCD, we derive the Boltzmann transport equation of quarkonium inside the quark-gluon plasma. Our derivation illuminates that the success of transport equations in quarkonium phenomenology is closely related to the separation of scales in the problem.
We report a recent calculation of the heavy quarkonium energy levels and decay widths in a quark- gluon plasma whose temperature is much smaller than the inverse radius of the bound state, based on a Non-Relativistic Effective Field theory framework for heavy quarkonium at finite temperature. Relevance for the phenomenology of the Y(1S) in heavy ion collisions is also discussed.
Production cross sections of heavy quarkonia are considered as useful tools to study various aspects of QCD. We have entered a new era of quarkonium production phenomenology, with the help of new measurements from the LHC giving access to more varieties of observables, and recent theoretical developments that provided us a better understanding of the short-distance process in which quarkonia are produced. With a more concrete understanding of perturbative corrections and a prolific collection of data, a satisfactory description of the quarkonium production mechanism might now be within reach. …
In this talk I review the calculation of the third order corrections to the heavy quarkonium spectrum in the nonrelativistic effective theory framework and its application to the phenomenology of top quark threshold production.
The FASTSUM collaboration has been carrying out simulations of N_f=2+1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.
We use the open quantum system formalism to study the dynamical in-medium evolution of quarkonium. The system of quarkonium is described by potential non-relativistic QCD while the environment is a weakly coupled quark-gluon plasma in local thermal equilibrium below the melting temperature of the quarkonium. Under the Markovian approximation, it is shown that the Lindblad equation leads to a Boltzmann transport equation if a Wigner transform is applied to the system density matrix. Our derivation illuminates how the microscopic time-reversibility of QCD is consistent with the time-irreversible…
We present the final results of our high statistics study on the properties of bottomonium and charmonium at finite temperature. We focus on the temperature range around the crossover transition $150\leq T\leq 410$MeV, relevant for current heavy ion collision experiments. The QCD medium degrees of freedom which consist of dynamical u,d, and s quarks and gluons are captured by realistic state-of-the art ($m_π\approx 161$MeV) lattice QCD simulations of the HotQCD collaboration. For the heavy quarks we deploy the non-relativistic effective field theory of QCD, NRQCD. The in-medium properties of q…
It is showed that potentials derived from classical solutions of the SU(3) Yang-Mills theory can provide confining potentials that reproduce the heavy quarkonium spectrum within the same level of precision as the Cornell potential.
We compute the total cross section of a heavy quarkonium on a hadron target in leading twist QCD, including target mass corrections. Our method relies on the analytical continuation of the operator product expansion of the scattering amplitude, obtained long ago by Bhanot and Peskin. The cross section has a simple partonic form, which allows us to investigate the phenomenology of J/psi and Upsilon dissociation by both pions and protons.
After discussing the intrinsic ambiguity in determining the light quark mass ratio $m_u/m_d$, we reexamine the recent proposal that this ambiguity can be resolved by applying the QCD multipole expansion for the heavy quarkonium decays. It is observed that, due to instanton effects, some matrix elements which have been ignored in previous works can give a significant contribution to the decay amplitudes, which results in a large uncertainty in the value of $m_u/m_d$ deduced from quarkonium phenomenology. This uncertainty can be resolved only by a QCD calculation of some second order coefficient…
We review the current status of heavy quarkonium production phenomenology based on nonrelativistic effective field theories, focusing on spin-triplet $S$-wave states such as $J/ψ$, $ψ(2S)$, and $Υ$. We present some representative examples for heavy quarkonium production mechanisms proposed in the literature, which vary significantly depending on the choice of data employed in analyses. We then discuss the rôle of polarization in discriminating between the different possible scenarios for quarkonium production. Other observables that may be useful in pinpointing the production mechanism are als…
We present a simple method to automatically evaluate arbitrary tree-level amplitudes involving the production or decay of a heavy quark pair QQbar in a generic {2S+1}L_J^[1,8] state, i.e., the short distance coefficients appearing in the NRQCD factorization formalism. Our approach is based on extracting the relevant contributions from the open heavy quark-antiquark amplitudes through an expansion with respect to the quark-antiquark relative momentum and the application of suitable color and spin projectors. To illustrate the capabilities of the method and its implementation in MadGraph a few a…
We study the mixing structure of isospin-singlet scalars, the light quarkonium $(\bar{q}q)$ and glueball $(gg)$ in two-flavor QCD, based on a holographic model of bottom-up hard-wall type. In the model the pure quarkonium and glueball states are unambiguously defined in terms of the different $U(1)_A$ charges in the restoration limit of the chiral $U(2)_L \times U(2)_R$ symmetry, in which the quarkonium gets massless as the chiral partner of the pion. Hence the $\bar{q}q$-$gg$ mixing arises in the presence of the nonzero chiral condensate or pion decay constant. At the realistic point where th…
Medium-Induced Quarkonium Dissociation at Finite Chemical Potential and Weak Magnetic Field
Discipline of Natural Sciences, PDPM IIITDM（PDPM印度理工学院德里曼德拉技术学院自然学系）；Department of Physics, Lords Institute of Engineering and Technology（洛兹工程技术学院物理系）；Key Laboratory of Quark and Lepton Physics (MOE) & Institute of Particle Physics, Central China Normal University（华中师范大学夸克与轻子物理教育部重点实验室及粒子物理研究所）；Department of Physics, Integral University（Integral大学物理系）；Department of Physics, Institute of Science, Banaras Hindu University (BHU)（贝拿勒斯印度教大学科学研究所物理系）
We extend previous calculations of leading-order correlation functions of spin-0 and spin-1 light quarkonium hybrids to include QCD condensates of dimensions five and six, with a view to improving the stability of QCD sum-rules analyses in previously unstable channels. Based on these calculations, prior analyses in the literature, and its phenomenological importance, we identify the exotic $J^{PC}=0^{+-}$ channel as the most promising for detailed study. Using Gaussian sum-rules constrained by the Hölder inequality, we calculate masses of light (nonstrange and strange) quarkonium hybrid mesons…
Many measurements of quarkonium suppression at the LHC, e.g. the nuclear modification factor $R_{AA}$ of $J/Ψ$, are well described by a multitude of different models. Thus pinpointing the underlying physics aspects is difficult and guidance based on first principles is needed. Here we present the current status of our ongoing high precision study of in-medium spectral properties of both bottomonium and charmonium based on NRQCD on the lattice. This effective field theory allows us to capture the physics of quarkonium without modeling assumptions in a thermal QCD medium. In our study a first pr…
We proceed to the first study of $η_c'$ prompt hadroproduction at next-to-leading order in $α_s$. Based on heavy-quark-spin symmetry, which is systematically used in quarkonium-production phenomenology, we demonstrate that prompt $η_c'$ can be studied at the LHC with the existing data. We emphasize its relevance to constrain $ψ'$ production, in the same way as the first prompt $η_c'$ data at the LHC lately strongly impacted the phenomenology of $J/ψ$ studies.
We present a two-flavour linear sigma model with global chiral symmetry and (axial-)vector mesons as well as an additional glueball degree of freedom. We study the structure of the well-established scalar resonances f0(1370) and f0(1500): by a fit to experimentally known decay widths we find that f0(1370) is predominantly a \bar{q}q state and f0(1500) is predominantly a glueball state. The overall phenomenology of these two resonances can be well described. Other assignments for our mixed quarkonium-glueball states are also tested, but turn out to be in worse agreement with the phenomenology. …
Within the supersymmetric SO(10) grand unified theory (GUT), a new mechanism, giving the light Higgs doublet as a pseudo-Goldstone mode, is suggested. Realizing this mechanism, we present an explicit model with fully realistic phenomenology. In particular, desirable symmetry breaking and natural all-order hierarchy are achieved. The constructed model allows one to have a realistic fermion pattern, nucleon stability, and successful gauge coupling unification. The suggested mechanism opens prospects in the field for a novel $SO(10)$ GUT model building and for further investigations.
Heavy quarkonium production in ultra-peripheral nuclear collisions (UPC) is described within the QCD dipole formalism. Realistic quarkonium wave functions in the $Q\bar Q$ rest frame are calculated by solving the Schrödinger equation with a subsequent Lorentz boost to high energy. We rely on several realistic $Q\bar Q$ potentials, which allow to describe well the quarkonium masses and decay widths, as well as data on diffractive electroproduction of quarkonia on protons. Nuclear effects are calculated with the phenomenological dipole cross sections fitted to DIS data. The higher twist quark sh…
The problem of quarkonium production in heavy ion collisions presents a set of unique theoretical challenges -- from the relevant production mechanism of $J/ψ$ and $Υ$ to the relative significance of distinct cold and hot nuclear matter effects in the observed attenuation of quarkonia. Inthese proceedings we summarize recent work on the generalization of non-relativistic Quantum Chromodynamics (NRQCD) to include off-shell gluon (Glauber/Coulomb) interactions in strongly interacting matter. This new effective theory provides for the first time a universal microscopic description of the in-mediu…
We present some of the topics covered in two lectures under the same title that were given at the "Summer School on High Energy Physics at the LHC: New trends in HEP" in Natal, Brazil. In this contribution we give a brief review on the application of perturbative QCD to the hard diffractive processes. Some examples of phenomenology for the diffractive production of $W/Z$, heavy $Q\bar{Q}$ and quarkonium in hadron-hadron reactions are presented. It is also discussed the exclusive diffractive processes in $ep$ interactions. They are in general driven by the gluon content of proton which is stron…
Extended technicolor (ETC) theories typically require ETC gauge bosons lighter than of order 1 TeV, to perturbatively generate the $t$ quark mass. We point out that explicit models of $t-b$ mass splitting also typically contain additional TeV scale ETC gauge bosons transforming in the {\it adjoint} of technicolor, leading to large weak-isospin-breaking effects observable in the $ρ$ parameter. Viable ETC models may thus require a lowest ETC scale of order 10 TeV, with relatively strong and finely tuned couplings to generate $m_t$. Such models do not generate observable corrections to the $Zb{\b…
Modern data is showing increasing evidence that the Universe is accelerating. So far, all attempts to account for the acceleration have required some fundamental dimensionless quantities to be extremely small. We show how a class of scalar field models (which may emerge naturally from superstring theory) can account for acceleration which starts in the present epoch with all the potential parameters O(1) in Planck units.
These lectures contain an introduction to the following topics: 1) Phenomenology of the hadron spectrum; 2) The static Wilson loop in perturbative and in lattice QCD. Confinement and the flux tube formation; 3) Non static properties: effective field theories and relativistic corrections to the quarkonium potential; 4) The QCD vacuum: minimal area law, Abelian projection and dual Meissner effect, stochastic vacuum.
Eclectic flavor groups arising from string compactifications combine the power of modular and traditional flavor symmetries to address the flavor puzzle. This top-down scheme determines the representations and modular weights of all matter fields, imposing strict constraints on the structure of the effective potential, which result in controlled corrections. We study the lepton and quark flavor phenomenology of an explicit, potentially realistic example model based on a T6/Z3xZ3 orbifold compactification of the heterotic string that gives rise to an Omega(2) eclectic flavor symmetry. We find t…
We investigate the phenomenology of the Randall-Sundrum radion in realistic models of electroweak symmetry breaking with bulk gauge and fermion fields, since the radion may turn out to be the lightest particle in such models. We calculate the coupling of the radion in such scenarios to bulk fermion and gauge modes. Special attention needs to be devoted to the coupling to massless gauge fields (photon, gluon), since it is well known that loop effects may be important for these fields. We also present a detailed explanation of these couplings from the CFT interpretation. We then use these coupli…
Heavy-flavor particles are believed to provide valuable probes of the medium produced in ultrarelativistic collisions of heavy nuclei. In this article we review recent progress in our understanding of the interactions of charm and bottom quarks in the Quark-Gluon Plasma (QGP). For individual heavy quarks, we focus on elastic interactions for which the large quark mass enables a Brownian motion treatment. This opens a unique access to thermalization mechanisms for heavy quarks at low momentum, and thus to their transport coefficients in the quark-gluon fluid. Different approaches to evaluate he…
We continue our study on the gravity duals for strongly coupled large N QCD with fundamental flavors both at zero and non-zero temperatures. The gravity dual at zero temperature captures the logarithmic runnings of the coupling constants at far IR and the almost conformal, albeit strongly coupled, behavior at the UV. The full UV completion of gauge theory is accomplished in the gravity side by attaching an AdS cap to the IR geometry described in our previous work. Attaching such an AdS cap is highly non-trivial because it amounts to finding the right interpolating geometry and sources that tak…
In the popular littlest Higgs model, T-parity can be broken by Wess-Zumino-Witten (WZW) terms induced by a strongly coupled UV completion. On the other hand, certain models with multiple scalar multiplets (called moose models) permit the implementation of an exchange symmetry (X-parity) such that it is not broken by the WZW terms. Here we present a concrete and realistic construction of such a model. The little Higgs model with X-Parity is a concrete and realistic implementation of this idea. In this contribution, the properties of the model are reviewed and the collider phenomenology is discu…
Composite Higgs models provide an elegant solution to the hierarchy problem present in the Standard Model (SM) and give an alternative pattern leading to the mechanism of Electro-Weak Symmetry Breaking (EWSB). We present an analysis of the Higgs boson production and decay within a recently proposed realistic realization of this general idea: the 4D Composite Higgs Model (4DCHM). Comparing our results with the latest Large Hadron Collider (LHC) data we show that the 4DCHM could provide an alternative explanation with respect to the SM of the LHC results pointing to the discovery of a Higgs-like…
We review the Nambu-Jona-Lasinio (NJL) approach to the dynamical breaking of chiral symmetry in Quantum Chromodynamics (QCD). The subjects treated in Part I include the vacuum structure of QCD, mass spectra and coupling constants of hadrons, flavor mixing in mesons, the violation of the OZI rule in baryons, and the validity of the chiral perturbation in QCD. A subtle interplay between the axial anomaly and the current-quark masses is shown to play important roles, and a realistic evaluation of the strangeness and heavy quark contents of hadrons is given. In Part II, the NJL model is applied to…
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 l…
We present the current status of the application of our approach of {\it exact} amplitude-based resummation in quantum field theory to precision QCD calculations, by realistic MC event generator methods, as needed for precision LHC physics.In this ongoing program of research, we discuss recent results as they relate to the interplay of the attendant IR-Improved DGLAP-CS theory of one of us and the precision of exact NLO matrix element matched parton shower MC's in the Herwig6.5 environment in relation to recent LHC experimental observations. There continues to be reason for optimism in the att…
Recently, we presented the first non-Abelian flat directions that produce from a heterotic string model solely the three-generation MSSM states as the massless spectrum in the observable sector of the low energy effective field theory. In this paper we continue to develop the systematic techniques for the analysis of nonrenormalizable superpotential terms and non-Abelian flat direction in realistic string models. Some of our non-Abelian directions were F-flat to all finite orders in the superpotential. We study for the same string model the varying phenomenologies resulting from a large set of…
We investigate the spontaneous breaking of chiral symmetry in QCD by means of a recently proposed approximation scheme in the Landau-gauge Curci-Ferrari model, which combines an expansion in the Yang-Mills coupling and in the inverse number of colors, without expanding in the quark-gluon coupling. The expansion allows for a consistent treatment of ultraviolet tails via renormalization group techniques. At leading order, it leads to the resummation of rainbow diagrams for the quark propagator, with, however, a trivial running of both the gluon mass and the quark-gluon coupling. In a previous wo…
We present simplified MSSM models for light neutralinos and charginos with realistic mass spectra and realistic gaugino-higgsino mixing, that can be used in experimental searches at the LHC. The formerly used naive approach of defining mass spectra and mixing matrix elements manually and independently of each other does not yield genuine MSSM benchmarks. We suggest the use of less simplified, but realistic MSSM models, whose mass spectra and mixing matrix elements are the result of a proper matrix diagonalisation. We propose a novel strategy targeting the design of such benchmark scenarios, ac…
The similarities of hadrons and atoms motivate a study of the principles of QED bound states and of their applicability to QCD. The power series in $α$ and $\logα$ of the binding energy is reflected in the Fock expansion of the bound state in temporal gauge ($A^0=0$). Gauss' constraint on physical states fixes the gauge for time independent transformations and determines the instantaneous interaction within each Fock state. Positronium atoms generate a classical (dipole) electric field, whereas there can be no color octet gluon field for color singlet hadrons. Hence the gluon field generated b…
We discuss theoretical and phenomenological aspects of two-Higgs-doublet extensions of the Standard Model. In general, these extensions have scalar mediated flavour changing neutral currents which are strongly constrained by experiment. Various strategies are discussed to control these flavour changing scalar currents and their phenomenological consequences are analysed. In particular, scenarios with natural flavour conservation are investigated, including the so-called type I and type II models as well as lepton-specific and inert models. Type III models are then discussed, where scalar flavo…
We study the possible phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in Type IIA string theory on the T^6/(Z2 x Z2) orientifold with some desirable semi-realistic features. In the model, tree-level gauge coupling unification is achieved automatically at the string scale, and the gauge symmetry may be broken to the Standard Model (SM) close to the string scale. The small number of extra chiral exotic states in the model may be decoupled via the Higgs mechanism and strong dynamics. We calculate the possible supersymmetry breaking soft terms and the corre…
We propose a new guiding principle for phenomenology: special geometry in the vacuum space. New algorithmic methods which efficiently compute geometric properties of the vacuum space of N=1 supersymmetric gauge theories are described. We illustrate the technique on subsectors of the MSSM. The fragility of geometric structure that we find in the moduli space motivates phenomenologically realistic deformations of the superpotential, while arguing against others. Special geometry in the vacuum may therefore signal the presence of string physics underlying the low-energy effective theory.
