Workshop JPAC & JLab12

18 Feb 2026, 08:00 → 20 Feb 2026, 18:00 Europe/Rome

Aula 603 (Dipartimento di Fisica, Università di Genova)

Alessandro Pilloni (UniME & INFN CT), Marco Battaglieri (Istituto Nazionale di Fisica Nucleare)

It is an exciting time for hadron spectroscopy. An extensive collection of new states have been observed in modern experiments, ranging from the light sector up to heavy quarkonia. When combined with the unprecedented amount of events collected, these results enable us to access a new plethora of phenomena.  An understanding of the dynamics that confines constituents are paramount to conceive the formation of the many unstable hadrons we observe. The extraction and identification of these short-lived states require elaborated analysis tools. The workshop aims at gathering experimentalists and theorists together to discuss the key points and future directions involving modern hadron spectroscopy, and will be centered on the JPAC and JLab12 activities 

This workshop is intended to be interactive, with ample time for discussions. We would like to encourage all participants to contribute their ideas to the various topics that will be presented.

Wednesday 18 February

Session

1 Greetings from the director

2 Spectroscopy at CLAS and CLAS12

The study of baryonic excited states provides fundamental information on the internal structure of the nucleon and on the degrees of freedom that are relevant for QCD at low energies. N* are composite states and are sensitive to details of the how quarks are confined. Meson photo-and electro-production reactions have provided complementary information on light quark baryon spectroscopy for several decades, but a crucial step forward has been the advent of large solid angle detectors, together with polarized beam and targets, which gave access to single and double polarization observables. The Q2 dependences of excited baryons electro-couplings have also been measured at CLAS, gaining insight into the internal structure of baryons.
The CLAS12 energy upgrade opened an “exciting” new era in baryon spectroscopy, including the search for hybrid hadrons, in which gluons appear as constituent components beyond the valence quarks.

Speaker: Annalisa D'Angelo (Istituto Nazionale di Fisica Nucleare)

DAngelo_Genova_2026.pptx

3 Beam Spin Asymmetry Preliminary Studies on KΛ(1520) electroproduction at CLAS12

An experimental program has been approved at the Thomas Jefferson National Accelerator Facility to study exclusive (KY) electroproduction with CLAS12 in order to search for new excited baryon states in the mass range ($W \simeq 1.8-3.0\text{ GeV}$). Two dedicated data-taking campaigns were carried out in 2018 and 2024. Although the 2018 dataset has limited statistics, it demonstrated excellent data quality and allowed for two publications: 2024 data will provides improved statistics and momentum resolution.
In this talk I will present preliminary results from the ($(ep,e'K^+)Y^*$) channel, with emphasis on the first steps of a beam–spin asymmetry (BSA) analysis using a longitudinally polarized electron beam and an unpolarized target.

Speaker: Chiara Ammendola (Istituto Nazionale di Fisica Nucleare)

presentazione Genova Chiara Ammendola.pdf

4 Extraction of polarization asymmetries in two pion photoproduction with circularly polarized beam

Speaker: Dr Alessandra Filippi (Istituto Nazionale di Fisica Nucleare sez. di Torino)

JPACJLAB12_AF_twoPiPolarization.pdf

15:40 Coffee break

5 Regge theory for pedestrians

Regge theory for pedestrian

Speaker: Andrzej Szczepanski

6 Regge exchanges in high energy photoproduction processes

I present the results from the amplitude analysis of the photoproduction of $\pi^{-}\Delta^{++}$. The GlueX data on the spin-density matrix elements of this process have been used to extract the phase relationship between the helicity amplitudes in a model independent way. Using the crossing relations and the principle of duality, the cross-channel residues and from them, the couplings for various meson exchanges have also been extracted.

Speaker: Vanamali Shastry (CEEM, IU Bloomington)

7 AI applications to pion scattering

Speaker: Wyatt Smith (Indiana University)

Thursday 19 February

Session

8 Elliptically Polarised PWA

Speaker: Derek Ian Glazier (University of Glasgow)

EllipticalPresentation.pdf

9 2 Pi production at Clas12

Analysis of 2 pions quasi-photoproduction at Clas12

Speaker: Marco Filippini (Istituto Nazionale di Fisica Nucleare)

10 Moments of Angular Distribution of K+K- with CLAS12

Since the prediction of the meson in 1935, facilities and institutions worldwide have contributed to the discovery of over 200 distinct types, including the pions, kaons, and J/Ψ. Meson spectroscopy involves understanding the properties of the mesons, allowing for the classification of this vast family of hadrons to be improved, which is particularly important for the discovery of new or exotic mesons – those forbidden in the naive quark model. In this endeavour, determining the spin of a meson is vitally important. A set of quantities known as moments of angular distributions provides information on the spin of a meson, which can be extracted from the angular distributions of its decay products. Jefferson Lab, located in Virginia, USA, is a high-luminosity, multi-GeV electron beam facility and is home to the CLAS12 detector, which is used to study the electro- and photo-production of meson resonances. This talk will present the preliminary results and novel analysis techniques developed for the extraction of moments of angular distributions of meson resonances decaying into a pair of oppositely charged kaons. These techniques involve improved particle identification based on the time-of-flight, cuts in longitudinal phase space to remove baryon resonances and the application of an MCMC-based algorithm. Preliminary moments of angular distributions will be shown, and properties of the resonances will be discussed.

Speaker: Charlie Velasquez (University of York)

JPAC Genoa February 2026.pdf

11:00 Coffee break

11 SDME and moments in electroproduction

Speaker: Dillon Leahy (University of Glasgow)

Electroprod_Genoa_Feb_2026.pdf

12 Discussion

Discussion points

Session

13 Diffusion model for unfolding CLAS detector

We introduce a novel strategy to unfold detector distortions in CLAS two-pion photoproduction measurements using a diffusion model. By training the model on simulated events, we enable it to recover the "true" kinematic distributions from reconstructed data, from which moment distributions can then be extracted. This approach improves the learning convergence rate and flexibility across different topologies, paving the way for extracting moments from real CLAS data.

Speaker: Giorgio Foti (Università di Messina & INFN Catania)

genova-jpac-jlab12-2026.pdf

14 Acceptance corrections with AI

Speaker: Marco Battaglieri (Istituto Nazionale di Fisica Nucleare)

Battaglieri-JPAC-JLAB12-GOA-Feb26.pdf

15 Discussion

16 Next steps for J/psi photoproduction

Since the JLab measurements of J/psi photoproduction near threshold in 2023, interest in the reaction has continued to increase with a plethora of new theoretical works attempting to interpret the dynamics underling the data. In light of JPAC's effort to model-independently disentangle the physics at play resulting inconclusive with the present statistics, I briefly examine possible avenues to maximize current data through the use of finite-energy sum rules and upcoming SDME measurements by GlueX.

Speaker: Daniel Winney (ICN-UNAM)

15:40 Coffee break

17 Spectroscopy at LHCb

Speakers: Elisabetta Spadaro Norella (Istituto Nazionale di Fisica Nucleare), Elisabetta Spadaro Norella (University of Genoa)

JPAC_SPADARO_19-2-26.pdf

18 The μCLAS12 Project

The μCLAS12 Project

Speaker: Mariangela Bondi (Istituto Nazionale di Fisica Nucleare)

WS_JPAC_Genova2026_MUCLAS.pdf

19 A Deuterium Target at μCLAS12

Speakers: Richard Tyson (University of Glasgow), Richard Tyson (University of Glasgow)

muCLAS12_wJPac.pdf

20 Spectroscopy opportunities at μCLAS12 Project

Spectroscopy opportunities at μCLAS12 Project

Speaker: Dr Alessandro Pilloni (UniME & INFN CT)

spectroscopy_muclas.pptx

21 Discussion

Friday 20 February

Session

22 Spectroscopy of Light and Heavy Baryons

Speaker: Elena Santopinto (Istituto Nazionale di Fisica Nucleare)

Jlab_2026_last.pdf

23 Finite Energy Sum Rules in Pi P --> Pi Eta(') P

In this talk, I will review the sum rules for 3 particle final state reactions and their recent application to the COMPASS data in Pi P --> Pi Eta(') P.

Speaker: Vincent Mathieu

Genoa.pdf

24 Reggeon exchange model for the $\pi^+\pi^-$ photoproduction - status and outlook

A model of the $\pi^+\pi^-$ photoproduction developed by JPAC will be discussed. The model's application for the description of moments of angular measured by CLAS collaboration at JLAB will be presented. Possible applications as well as extensions to other di-pseudoscalar channels (like $K^+K^-$) will be outlined.

Speaker: Łukasz Bibrzycki (AGH University of Krakow)

11:00 Coffee break

25 Pion Exchange

Speaker: Gloria Montana (University of Barcelona, Institute of Cosmos Sciences (ICCUB))

2026_workshopJPACandJLab12_GloriaMontana.pdf

26 Incorporating the RICH into CLAS12 Analyses

Speaker: Simone Vallarino (Istituto Nazionale di Fisica Nucleare)

Vallarino_2026_02_20.pdf

27 Discussion