SearcharxivSearch

arXiv subjects

B. Blossier

Publications and source records attributed to B. Blossier.

At least 19 recordsLinked to original sources

2025 EIC-France Workshop: Physics Highlights and Perspectives

This document presents a synthesis of the theory contributions and discussions from the 2nd EIC-France Workshop, held at IJCLab (Orsay) on 1-3 December 2025. The workshop brought together members of the French hadron-physics community to review recent theoretical developments relevant to the future Electron-Ion Collider (EIC) and to coordinate national efforts in preparation for its early physics program. The report first summarizes the collider's initial running conditions and luminosity performance, as outlined in the EIC Early Science Matrix. It then provides concise overviews of the theoretical presentations on inclusive, semi-inclusive, exclusive, heavy-flavor, and small-x physics. Based on these discussions, two measurements emerged as especially well suited for early EIC operation and strongly aligned with areas of established French expertise: inclusive diffraction and inclusive quarkonium production. These channels offer clean signatures, robust theoretical interpretability, and direct sensitivity to fundamental QCD phenomena such as gluon saturation, heavy-quark dynamics, and the small-x structure of hadrons and nuclei. In addition, the workshop identified longer-term physics opportunities that will benefit from the full capabilities of the EIC after its ramp-up phase. These include accessing the three-dimensional structure of the pion through the Sullivan process and a broader program of exclusive three-body final states, both of which represent high-impact avenues for exploring hadronic structure and non-perturbative QCD. Together, the elements summarized in this report provide a coherent overview of the strategic priorities and scientific ambitions shaping the French community's contribution to the EIC physics program.

hep-ph

Lattice QCD extraction of the $\eta_{c}$-meson $t$-dependent parton distribution function

The formalism of short-distance factorization, conveyed through the pseudo-distribution approach, connects space-like and light-cone correlators and thus allows for the extraction in lattice QCD of a number of parton distributions. We compute the $t$-dependent parton distribution function of valence quarks in a $\eta_{c}$-meson. After reviewing the main ideas behind the pseudo-distribution formalism, and relying on the analytic structure of Ioffe-time distributions, we come up with a proposal for a model-independent extraction of $t$-dependent parton distribution functions. We present results for the $\eta_{c}$-meson Ioffe time valence $t$-dependent parton distribution function at a renormalization scale of $3~\textrm{GeV}$.

hep-lat

Semileptonic $B \to D^{**}$ decays in Lattice QCD : a feasibility study and first results

We compute the decays ${B\to D^\ast_0}$ and ${B\to D^\ast_2}$ with finite masses for the $b$ and $c$ quarks. We first discuss the spectral properties of both the $B$ meson as a function of its momentum and of the $D^\ast_0$ and $D^\ast_2$ at rest. We compute the theoretical formulae leading to the decay amplitudes from the three-point and two-point correlators. We then compute the amplitudes at zero recoil of ${B\to D^\ast_0}$ which turns out not to be vanishing contrary to what happens in the heavy quark limit. This opens a possibility to get a better agreement with experiment. To improve the continuum limit we have added a set of data with smaller lattice spacing. The ${B\to D^\ast_2}$ vanishes at zero recoil and we show a convincing signal but only slightly more than 1 sigma from 0. In order to reach quantitatively significant results, we plan to fully exploit smaller lattice spacings as well as another lattice regularization.

hep-lat

Decay constants of B-mesons from non-perturbative HQET with two light dynamical quarks

We present a computation of B-meson decay constants from lattice QCD simulations within the framework of Heavy Quark Effective Theory for the b-quark. The next-to-leading order corrections in the HQET expansion are included non-perturbatively. Based on Nf=2 gauge field ensembles, covering three lattice spacings a (0.08-0.05)fm and pion masses down to 190MeV, a variational method for extracting hadronic matrix elements is used to keep systematic errors under control. In addition we perform a careful autocorrelation analysis in the extrapolation to the continuum and to the physical pion mass limits. Our final results read fB=186(13)MeV, fBs=224(14)MeV and fBs/fB=1.203(65). A comparison with other results in the literature does not reveal a dependence on the number of dynamical quarks, and effects from truncating HQET appear to be negligible.

hep-lat

High statistics determination of the strong coupling constant in Taylor scheme and its OPE Wilson coefficient from lattice QCD with a dynamical charm

This paper reports on the determination of $α_S$ from lattice simulations with 2+1+1 twisted-mass dynamical flavours {\it via} the computation of the ghost-gluon coupling renormalized in the MOM Taylor scheme. A high-statistics sample of gauge configurations, used to evaluate the coupling from ghost and gluon propagators, allows for the appropriate update of previous results, now performing an improved analysis of data with reduced statistical errors and the systematical uncertainties under a better control.

hep-ph

The strong running coupling at $τ$ and $Z_0$ mass scales from lattice QCD

This letter reports on the first computation, from data obtained in lattice QCD with $u,d,s$ and $c$ quarks in the sea, of the running strong coupling via the ghost-gluon coupling renormalized in the MOM Taylor scheme. We provide with estimates of $\ams(m_τ^2)$ and $\ams(m_Z^2)$ in very good agreement with experimental results. Including a dynamical c quark makes safer the needed running of $\ams$.

hep-ph

The b-quark mass from non-perturbative $N_f=2$ Heavy Quark Effective Theory at $O(1/m_h)$

We report our final estimate of the b-quark mass from $N_f=2$ lattice QCD simulations using Heavy Quark Effective Theory non-perturbatively matched to QCD at $O(1/m_h)$. Treating systematic and statistical errors in a conservative manner, we obtain $\overline{m}_{\rm b}^{\overline{\rm MS}}(2 {\rm GeV})=4.88(15)$ GeV after an extrapolation to the physical point.

hep-lat

A novel method for the physical scale setting on the lattice and its application to $N_f$=4 simulations

This letter reports on a new procedure for the lattice spacing setting that takes advantage of the very precise determination of the strong coupling in Taylor scheme. Although it can be applied for the physical scale setting with the experimental value of $Λ_{\overline{\rm MS}}$ as an input, the procedure is particularly appropriate for relative "calibrations". The method is here applied for simulations with four degenerate light quarks in the sea and leads to prove that their physical scale is compatible with the same one for simulations with two light and two heavy flavours.

hep-lat

B decays to radially excited D

We discuss the possibility to measure in present experiments, especially LHCb, the non leptonic decay branching ratio $B \to D' π$, and emphasize phenomenological implications on $B \to D' l ν$ semileptonic decay. We have estimated by lattice QCD the $D'$ decay constant $f_{D'}$ that parameterizes the $D'$ emission contribution to the Class-III non leptonic decay $B^- \to D^0 π^-$. In addition, we provide a new estimate of the decay constants $f_{D_{s,q}}$ which read $f_{D_{s}}=252(3)$ MeV and $f_{D_{s}}/f_{D}=1.23(1)(1)$.

hep-lat

B-physics with $N_f=2$ Wilson fermions

We report the final results of the ALPHA collaboration for some B-physics observables: $f_B$, $f_{B_s}$ and $m_b$. We employ CLS configurations with 2 flavors of $O(a)$ improved Wilson fermions in the sea and pion masses ranging down to 190 MeV. The b-quark is treated in HQET to order $1/m_b$. The renormalization, the matching and the improvement were performed non-perturbatively, and three lattice spacings reaching $a=0.048$ fm are used in the continuum extrapolation.

hep-lat

Lattice measurement of α_s with a realistic charm quark

We report on an estimate of α_s, renormalised in the MSbar scheme at the tau and Z^0 mass scales, by means of lattice QCD. Our major improvement compared to previous lattice calculations is that, for the first time, no perturbative treatment at the charm threshold has been required since we have used statistical samples of gluon fields built by incorporating the vacuum polarisation effects of u/d, s and c sea quarks. Extracting α_s in the Taylor scheme from the lattice measurement of the ghost-ghost-gluon vertex, we obtain α_s^{MSbar}(m^2_Z)=0.1200(14) and α_s^{MSbar}(m^2_tau)=0.339(13).

hep-lat

Testing the OPE Wilson coefficient for $A^2$ from lattice QCD with a dynamical charm

Gluon and ghost propagators data, obtained in Landau gauge from lattice simulations with two light and two heavy dynamical quark flavours ($N_f$=2+1+1), are described here with a running formula including a four-loop perturbative expression and a nonperturbative OPE correction dominated by the local operator $A^2$. The Wilson coefficients and their variation as a function of the coupling constant are extracted from the numerical data and compared with the theoretical expressions that, after being properly renormalized, are known at ${\cal O}(α^4)$. As also $Λ_{\msbar}$ is rather well known for $N_f$=2+1+1, this allows for a precise consistency test of the OPE approach in the joint description of different observables.

hep-ph

$|V_{ub}|$ determination in lattice QCD

The 2012 PDG reports a tension at the level of $3 σ$ between two exclusive determinations of $|V_{ub}|$. They are obtained by combining the experimental branching ratios of $B \to τν$ and $B \to πl ν$ (respectively) with a theoretical computation of the hadronic matrix elements $\fB$ and the $B \to π$ form factor $f_+(q^2)$. To understand the tension, improved precision and a careful analysis of the systematics involved are necessary. We report the results of the ALPHA collaboration for $\fB$ from the lattice with 2 flavors of $O(a)$ improved Wilson fermions. We employ HQET, including $1/m_b$ corrections, with pion masses ranging down to $\approx$ 190 MeV. Renormalization and matching were performed non-perturbatively, and three lattice spacings reaching $a^{-1}\approx 4.1$ GeV are used in the continuum extrapolation. We also present progress towards a computation of $f_+(q^2)$, to directly compare two independent exclusive determinations of $|V_{ub}|$ with each other and with inclusive determinations. Additionally, we report on preliminary results for $\fBq{s}$, needed for the analysis of $B_s \to μ^+μ^-$.}

hep-lat

B-physics from HQET in two-flavour lattice QCD

We present our analysis of B physics quantities using non-perturbatively matched Heavy Quark Effective Theory (HQET) in Nf= 2 lattice QCD on the CLS ensembles. Using all-to-all propagators, HYP-smeared static quarks, and the Generalized Eigenvalue Problem (GEVP) approach with a conservative plateau selection procedure, we are able to systematically control all sources of error. With significantly increased statistics compared to last year, our preliminary results are mb (mb) = 4.22(10)(4)z GeV for the MS b-quark mass, and fB = 193(9)stat (4)_χMeV and fBs = 219(12)stat MeV for the B-meson decay constants.

hep-lat

Ghost-gluon coupling, power corrections and $Λ_{\bar{\rm MS}}$ from lattice QCD with a dynamical charm

This paper is a first report on the determination of $Λ_{\msbar}$ from lattice simulations with 2+1+1 twisted-mass dynamical flavours {\it via} the computation of the ghost-gluon coupling renormalized in the MOM Taylor scheme. We show this approach allows a very good control of the lattice artefacts and confirm the picture from previous works with quenched and ${\rm N}_f$=2 twisted-mass field configurations which prove the necessity to include non-perturbative power corrections in the description of the running. We provide with an estimate of $Λ_{\msbar}$ in very good agreement with experimental results. To our knowledge it is the first calculation with a dynamical charm quark which makes the running up to $α_s(M_Z)$ much safer.

hep-lat

Renormalisation constants of quark bilinears in lattice QCD with four dynamical Wilson quarks

We present preliminary results of the non-perturbative computation of the RI-MOM renormalisation constants in a mass-independent scheme for the action with Iwasaki glue and four dynamical Wilson quarks employed by ETMC. Our project requires dedicated gauge ensembles with four degenerate sea quark flavours at three lattice spacings and at several values of the standard and twisted quark mass parameters. The RI-MOM renormalisation constants are obtained from appropriate O(a) improved estimators extrapolated to the chiral limit.

hep-lat

RI/MOM renormalization constants (N_f=4) and the strong coupling constant (N_f=2+1+1) from twisted-mass QCD

We study RI/MOM renormalization constants of bilinear quark operators for $N_f=4$ and the strong coupling constant for $N_f=2+1+1$ using Wilson twisted-mass fermions. We use the "egalitarian" method to remove H(4) hypercubic artifacts non-perturbatively, which enables us to study physical quantities in a wide range of momenta. We then apply OPE in studying the running behavior of $Z_q$ and $α_s$, from which we are able to extract the Landau gauge dimension-two gluon condensate $ $ which is of phenomenological interest.

hep-lat

Vacuum expectation value of A^2 from LQCD

We argue from LQCD that there is a non vanishing v.e.v of $A_a^μA^a_μ$ in QCD in the Landau gauge. We use operator product expansion to provide a clear definition of $A_a^μA^a_μ$ and extract a number both in the quenched and unquenched case.

hep-lat