arXiv subjects

Vincent Mathieu

Publications and source records attributed to Vincent Mathieu.

At least 37 records · Page 2Linked to original sources

arXiv2018

Studying the Pc(4450) resonance in J/psi photoproduction off protons

The LHCb has reported the observation of a resonancelike structure, the Pc(4450), in the J/psi p invariant masses. In our work, we discuss the feasibility of detecting this structure in J/psi photoproduction, e.g. in the measurements that have been approved for the experiments in Hall A/C and in Hall B with CLAS12 at JLab. Also the GlueX Collaboration has already reported preliminary results. We take into account the experimental resolution effects, and perform a global fit to world J/psi photoproduction data in order to study the possibility of observing the Pc(4450) signal in future JLab data. We present a first estimate of the upper limit for the branching ratio of the Pc(4450) into the J/psi p channel, and we study the angular distributions of the differential cross sections. This will shed light on the nature and couplings of the Pc(4450) structure in the future photoproduction experiments.

hep-ph↗

arXiv2016

Understanding the Nature of $Λ(1405)$ through Regge Physics

It appears that there are two resonances with $J^P= 1/2^-$ quantum numbers in the energy region near the $Λ(1405)$ hyperon. The nature of these states is a topic of current debate. To provide further insight we use Regge phenomenology to access how these two resonances fit the established hyperon spectrum. We find that only one of these resonances is compatible with a three-quark state.

hep-ph↗

arXiv2016

The Joint Physics Analysis Center Website

The Joint Physics Analysis Center is a collaboration between theorists and experimentalists working in hadronic physics. In order to facilitate the exchange of information between the different actors in hadron spectroscopy, we created an interactive website. In this note, I summarize the first projects available on the website.

hep-ph↗

arXiv2013

Regge Amplitudes for Two-to-Two Reactions

We present a fit based on Regge theory of two-to-two reactions at high energies particulary focused on leading non-strange positive naturality exchanges. Factorization of the residues is assumed between beam and target vertices. This study is a first step toward the analysis of multiple mesons peripherical production.

hep-ph↗

arXiv2012

Collimation of energy in medium-modified QCD jets

The collimation of energy inside medium-modified jets is investigated in the leading logarithmic approximation of QCD. The Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution equations are slightly modified by introducing splitting functions enhanced in the infrared sector. As compared to elementary collisions in the vacuum, the angular istribution of the jet energy is found to broaden in QCD media.

hep-ph↗

arXiv2011

Three-particle correlations in QCD parton showers

Three-particle correlations in quark and gluon jets are computed for the first time in perturbative QCD. We give results in the double logarithmic approximation and the modified leading logarithmic approximation. In both resummation schemes, we use the formalism of the generating functional and solve the evolution equations analytically from the steepest descent evaluation of the one-particle distribution. We thus provide a further test of the local parton hadron duality and make predictions for the LHC.

hep-ph↗

arXiv2011

Three-particle correlations in QCD jets and beyond

In this paper, we present a more detailed version of our previous work for three-particle correlations in quark and gluon jets [1]. We give theoretical results for this observable in the double logarithmic approximation and the modified leading logarithmic approximation. In both resummation schemes, we use the formalism of the generating functional and solve the evolution equations analytically from the steepest descent evaluation of the one-particle distribution. In addition, in this paper we include predictions beyond the limiting spectrum approximation and study this observable near the hump of the single inclusive distribution. We thus provide a further test of the local parton hadron duality (LPHD) and make predictions for the LHC. The computation of higher rank correlators is presented in the double logarithmic approximation and shown to be rather cumbersome.

hep-ph↗

arXiv2011

Gluon Mass, Glueballs and Gluonic Mesons

We review the phenomenological and theoretical evidences for dynamical gluon mass generation and the main features of the glueball spectrum in (pure gauge) Yang-Mills theories. The mixing between glueball and conventional $\bar q q$ states in $f_0$ scalar mesons is discussed. For pseudoscalar mesons, the inclusion of the glue field in an effective low energy theory is presented leading to a third isoscalar $η''$ partner of the $η$ and $η'$. Branching ratios for processes involving $η''$ are given and, when available, compatible with data for $η(1405)$.

hep-ph↗

arXiv2010

Heavy quark flavour dependence of multiparticle production in QCD jets

After inserting the heavy quark mass dependence into QCD partonic evolution equations, we determine the mean charged hadron multiplicity and second multiplicity correlators of jets produced in high energy collisions. We thereby extend the so-called dead cone effect to the phenomenology of multiparticle production in QCD jets and find that the average multiplicity of heavy-quark initiated jets decreases significantly as compared to the massless case, even taking into account the weak decay products of the leading primary quark. We emphasize the relevance of our study as a complementary check of $b$-tagging techniques at hadron colliders like the Tevatron and the LHC.

hep-ph↗

arXiv2010

$η-η^\prime$ Mixing in the Flavor Basis and Large N

The mass matrix for $η-η^\prime$ is derived in the flavor basis at ${\cal O}(p^4)$ of the chiral Lagrangian using the large $N$ approximation. Under certain assumptions, the mixing angle $ϕ=41.4^\circ$ and the decay constants ratio $f_K/f_π=1.15$ are calculated in agreement with the data. It appears that the FKS scheme arises as a special limit of the chiral Lagrangian. Their mass matrix is obtained without the hypothesis on the mixing pattern of the decay constants.

hep-ph↗

arXiv2009

How Many Degrees of Freedom Has the Gluon ?

In constituent models, glueballs are described as bound states of effective gluons. The dynamical mass generation lead to a gluon mass without violating gauge invariance. One can then consider three degrees of freedom for those effective massive gluons. However, models with only two degrees of freedom are shown to be in better agreement with the lattice glueball spectrum. I review both models for two- and three-gluon models and explain why even though the gluon gains a mass, it behaves as a massless particle with only two degrees of freedom.

hep-ph↗

arXiv2009

Glueball phenomenology and the relativistic flux tube model

The relativistic flux tube model is an effective description of confined quarks and gluons in which the confining interaction is carried by the flux tube, a Nambu-Goto string. We first show that the relativistic flux tube model can be applied to glueballs seen as bound states of transverse constituent gluons. After a comparison of that approach with usual spinless Salpeter Hamiltonians, we compute glueball masses and decay widths. Comments about the $η$-$η'$-pseudosclar glueball problem, the glueball--Pomeron conjecture, and finite-temperature effects are finally given. We also point out the existence of a duality between open- and closed-flux tube models of glueballs.

hep-ph↗

arXiv2009

Hybrid meson masses and the correlated Gaussian basis

We revisited a model for charmonium hybrid meson with a magnetic gluon [Yu. S. Kalashnikova and A. V. Nefediev, Phys. Rev. D {\bf 77}, 054025 (2008)] and improved the numerical calculations. These improvements support the hybrid meson interpretation of X(4260). Within the same model, we computed the hybrid meson mass with an electric gluon which is resolved to be lighter. Relativistic effects and coupling channels decreased also the mass.

hep-ph↗

arXiv2008

The Physics of Glueballs

Glueballs are particles whose valence degrees of freedom are gluons and therefore in their description the gauge field plays a dominant role. We review recent results in the physics of glueballs with the aim set on phenomenology and discuss the possibility of finding them in conventional hadronic experiments and in the Quark Gluon Plasma. In order to describe their properties we resort to a variety of theoretical treatments which include, lattice QCD, constituent models, AdS/QCD methods, and QCD sum rules. The review is supposed to be an informed guide to the literature. Therefore, we do not discuss in detail technical developments but refer the reader to the appropriate references.

hep-ph↗

arXiv2008

Introduction to the Pinch Technique

These notes are a short introduction to the pinch technique. We present the one-loop calculations for basic QCD Green's functions. The equivalence between the pinch technique and the background field method is explicitly shown at the one-loop level. We review the absorptive pinch technique in the last sections. These lectures are a compilation of relevant papers on this subject and are prepared for the third Modave Summer School in Mathematical Physics.

hep-ph↗

arXiv2007

Spin dependent operators in correlated gaussian bases

In their textbook, Suzuki and Varga [Y. Suzuki and K. Varga, {\em Stochastic Variational Approach to Quantum-Mechanical Few-Body Problems} (Springer, Berlin, 1998)] present the stochastic variational method with the correlated Gaussian basis in a very exhaustive way. The matrix elements for central potentials are put under a pleasant form but the elements for spin dependent operators, when treated, are given as very cumbersome expressions. In this paper, we find a lot of new formulae for those elements. Their expressions are given in terms of the same geometrical functions that appear in the case of central potentials. These functions get therefore a universal status; this property is very useful for numerical applications.

physics.comp-ph↗

arXiv2007

Short-range potentials from QCD at order $g^2$

We systematically compute the effective short-range potentials arising from second order QCD-diagrams related to bound states of quarks, antiquarks, and gluons. Our formalism relies on the assumption that the exchanged gluons are massless, while the constituent gluons as well as the lightest quarks acquire a nonvanishing constituent mass because of confinement. The potentials we obtain include the first relativistic corrections, thus spin-spin terms, spin-orbit terms, etc. Such effective potentials are expected to be relevant for the building of accurate potential models describing usual hadrons as well as exotic ones like glueballs and $q\bar q g$ hybrids. In particular, we compute for the first time an effective quark-gluon potential, and show the existence of a quadrupolar interaction term in this case. We also discuss the influence of a possible nonzero mass for the exchanged gluons.

hep-ph↗

arXiv2007

The few-body problem in terms of correlated gaussians

In their textbook, Suzuki and Varga [Y. Suzuki and K. Varga, {\em Stochastic Variational Approach to Quantum-Mechanical Few-Body Problems} (Springer, Berlin, 1998)] present the stochastic variational method in a very exhaustive way. In this framework, the so-called correlated gaussian bases are often employed. General formulae for the matrix elements of various operators can be found in the textbook. However the Fourier transform of correlated gaussians and their application to the management of a relativistic kinetic energy operator are missing and cannot be found in the literature. In this paper we present these interesting formulae. We give also a derivation for new formulations concerning central potentials; the corresponding formulae are more efficient numerically than those presented in the textbook.

hep-ph↗