📄 New Preprint on arXiv!

Title: Moderate-to-Large-x Gluon Helicity from J/ψ Production at √s = 27 GeV Authors: Shubham Sharma (Moscow, ITEP & MIPT), Alexey Aparin (Moscow, ITEP & MIPT & JINR & Inst. Nucl. Phys., Almaty), Satyajit Puhan (Taiwan, Inst. Phys.), Narinder Kumar (M.N. College), Harleen Dahiya (Ambedkar, Nat. Inst. Technol.) e-Print: 2605.30945 [hep-ph] Pages: 5 pages

Key Highlights

• 🔹 First projection for constraining moderate-to-large-x gluon helicity distribution Δg(x) via J/ψ production at NICA-SPD energy
• 🔹 Color-singlet model at LO in perturbative QCD used to compute longitudinal double-spin asymmetry (A_LL)
• 🔹 Five NLO helicity PDF sets evaluated — NNPDFpol1.1, DSSV14, JAM17, LSS10, and AAL19
• 🔹 A_LL as a function of p_T and rapidity — significant discriminating power between different helicity PDF scenarios
• 🔹 Targeted regime: moderate-to-large-x (x ≳ 0.1), poorly constrained by existing RHIC and EIC data

Significance

This work establishes J/ψ production at √s = 27 GeV as a powerful probe for constraining the gluon helicity distribution, directly relevant for the upcoming SPD experiment at the NICA collider facility.

#GluonHelicity #JPsi #NICA #SPD #SpinPhysics #QCD #HelicityPDFs

🎉 Paper Accepted in Physical Review D!

Title: Spectroscopy of ρ-meson in symmetric nuclear medium Authors: Anshu Gautam, Tanisha, Satyajit Puhan, Arvind Kumar, Harleen Dahiya Affiliations: Ambedkar, Nat. Inst. Technol. Journal: Physical Review D (Accepted) e-Print: 2601.11082 [hep-ph]

Key Highlights

• 🔹 In-medium ρ-meson properties — mass, decay constant, and distribution amplitudes at finite baryonic density
• 🔹 Leading-twist DAs evolved via LO Efremov-Radyushkin-Brodsky-Lepage method
• 🔹 Mellin moments and decay width of ρ⁰ → e⁺e⁻ predicted in both vacuum and medium
• 🔹 Electromagnetic form factors — charge G_C(Q²), magnetic G_M(Q²), and quadrupole G_Q(Q²) in medium
• 🔹 Charge radii, magnetic and quadrupole moments predicted — weaker sensitivity to baryonic density
• 🔹 Significant medium modifications found for mass, decay constant, decay width, and DAs

Significance

This work provides a comprehensive investigation of the ρ-meson in symmetric nuclear matter, bridging light-front dynamics with finite-density nuclear physics.

Congratulations to the team! 🎉

#RhoMeson #NuclearMedium #FormFactors #DistributionAmplitudes #PRD #QCD

📄 New Preprint on arXiv!

Title: An Analysis on the Parton Distribution Functions of Heavy Mesons Author: Satyajit Puhan Affiliations: Computational High Energy Physics Lab, Dr. B.R. Ambedkar NIT, Jalandhar & Institute of Physics, Academia Sinica, Taipei, Taiwan e-Print: 2605.17389 [hep-ph]

Key Highlights

• 🔹 Constituent PDFs of the kaon and heavy pseudoscalar mesons (D⁺, Dₛ⁺, Bc⁺, ηc, ηb, B⁺, Bₛ⁰) within the light-cone quark model
• 🔹 NLO DGLAP evolution of initial-scale quark and antiquark PDFs to higher energy scales
• 🔹 Kaon NLO structure functions predicted at energy scales relevant for the upcoming Electron–Ion Collider (EIC)
• 🔹 Drell–Yan cross-section predictions for COMPASS++/AMBER with Carbon, Tungsten, and Aluminum nuclear targets for both isospin states of the kaon
• 🔹 Heavy quark dominance demonstrated — heavier constituents carry larger momentum fractions within their respective heavy mesons
• 🔹 Mellin moment ratios compared with lattice QCD and available theoretical models

Significance

This is a comprehensive, solo-author investigation bridging the internal structure of light and heavy mesons, providing essential predictions for the EIC and COMPASS++/AMBER experimental programs.

#HeavyMesons #PDFs #LCQM #DGLAP #EIC #COMPASS #AMBER #DrellYan #QCD

🎉 Paper Accepted in PTEP!

Title: Valence quark distribution of the pion inside a medium with finite baryon density: A Nambu–Jona-Lasinio model approach Authors: Ashutosh Dwibedi (IIT Bhilai), Satyajit Puhan (Ambedkar NIT), Sabyasachi Ghosh (IIT Bhilai), Harleen Dahiya (Ambedkar NIT) Journal: Progress of Theoretical and Experimental Physics (PTEP) e-Print: 2512.24921 [hep-ph]

Key Highlights

• 🔹 In-medium pion PDFs calculated using the light-cone quark model with medium-modified constituent quark masses
• 🔹 Two-flavor NJL model employed to obtain constituent quark masses at finite baryon density
• 🔹 NLO DGLAP evolution of in-medium parton distribution functions from model scale to perturbative scale
• 🔹 Electromagnetic form factors compared with experimental measurements and lattice QCD
• 🔹 Mellin moments examined in comparison with existing extractions and theoretical model predictions
• 🔹 Distribution amplitudes and in-medium modifications of pion properties

Significance

This work bridges nuclear medium effects with light-front dynamics, providing the first systematic study of pion PDFs at finite baryon density using the NJL model within the LCQM framework.

Congratulations to the team! 🎉

#PionPDFs #NJLModel #NuclearMedium #DGLAP #PTEP #QCD

🎤 Seminar at Prof. C. R. Ji's Research Group

Talk Title: Extraction of Pion GPDs Speaker: Satyajit Puhan Affiliation: IOP, Academia Sinica, Taipei, Taiwan Group: Prof. C. R. Ji's Research Group, NCSU, USA Mode: Zoom Meeting Date: 17th April, 2026

Talk Highlights

• 🔹 Data-driven extraction of pion unpolarized quark GPDs at zero skewness (ξ = 0) from a global fit to experimental pion form factor and PDF measurements
• 🔹 Flexible form factor parameterization embedded into a GPD framework with collinear PDFs and a profile function encoding transverse dynamics
• 🔹 Impact-parameter-space interpretations — spatial parton distributions revealing the internal structure of the lightest QCD bound state
• 🔹 Interactive parameter explorer — live demonstration of the Pion Form Factor Interactive Parameter Explorer tool
• 🔹 Essential input for future experiments — EIC Sullivan process, JLab 12 GeV, COMPASS, and AMBER pion-beam experiments

Connection to Previous Work

This is the second seminar at Prof. C. R. Ji's group. The first seminar (July 2025) covered the broader internal structure of light mesons through distribution functions (PDFs, GPDs, TMDs, and mechanical properties). This talk focuses specifically on the recent data-driven extraction of pion GPDs from charge form factors.

#PionGPDs #FormFactor #ImpactParameter #SullivanProcess #EIC #JLab #COMPASS #AMBER #QCD

📄 New Preprint on arXiv!

Title: Extraction of Pion Unpolarized Quark Generalized Parton Distribution from Charge Form Factors Authors: Satyajit Puhan (Taiwan, Inst. Phys.), Shubham Sharma (Moscow, ITEP & MIPT), Narinder Kumar (Ambedkar NIT & M.N. College), Harleen Dahiya (Ambedkar NIT) e-Print: 2604.11116 [hep-ph]

Key Highlights

• 🔹 Data-driven extraction of pion unpolarized quark GPDs at zero skewness (ξ = 0) from a global fit to experimental pion form factor and PDF measurements
• 🔹 Flexible form factor parameterization embedded into a GPD framework with collinear PDFs and a profile function encoding transverse dynamics
• 🔹 Impact-parameter-space interpretations — spatial parton distributions revealing the internal structure of the lightest QCD bound state
• 🔹 Essential input for future experiments — EIC Sullivan process, JLab 12 GeV exclusive π⁺ electroproduction, COMPASS, and AMBER pion-beam experiments
• 🔹 Lattice QCD connections — results provide benchmarks for phenomenological and lattice investigations of meson structure

Significance

This work provides a unified description of the pion's electromagnetic structure and spatial parton distributions, bridging global QCD fits with next-generation collider and fixed-target experiments.

#PionGPDs #FormFactor #ImpactParameter #SullivanProcess #EIC #JLab #COMPASS #AMBER #QCD

📄 arXiv Preprint Now Available!

Title: Internal Structure of Light Mesons Using the Power Law Wave Function Authors: Satyajit Puhan, Narinder Kumar, Harleen Dahiya Published in: Modern Physics Letters A (2026), World Scientific — Special Issue (Guest Editor: Dr. Parada Hutauruk) e-Print: 2604.07049 [hep-ph]

Key Results

• 🔹 Distribution Amplitudes, PDFs, TMDs, GPDs, and Form Factors for pion and kaon using spin-improved power-law wave functions
• 🔹 ERBL and NLO DGLAP evolution — only 41% longitudinal momentum carried by quarks at 16 GeV²
• 🔹 Charge radii: r_π = 0.668 fm and r_K = 0.704 fm
• 🔹 Good agreement with NA7, FNAL, JLab, and E615 experimental data

#PowerLaw #PionStructure #KaonStructure #LightFront #FormFactors #QCD

📄 New Preprint on arXiv!

Title: Pion Parton Distribution Functions in the Light-Cone Quark Model and Experimental Constraints Authors: Hari Govind P, Satyajit Puhan, Abhishek K. P, Reetanshu Pandey, Harleen Dahiya, Suneel Dutt, Arvind Kumar e-Print: 2604.05762 [hep-ph] Pages: 21 pages, 15 figures, 4 tables

Key Highlights

• 🔹 Pion valence quark PDFs calculated within the light-cone quark model (LCQM) using quark-quark correlation functions
• 🔹 NLO DGLAP evolution of initial-scale PDFs to higher energy scales
• 🔹 First prediction of pion F₂ structure function at NLO — compared with ZEUS and H1 data at DESY-HERA
• 🔹 Drell-Yan cross-sections for forward pion production using LHAPDF nucleon PDF datasets
• 🔹 EIC projections — F₂ structure function studied at electron-ion collider kinematics

Significance

This work bridges theoretical predictions from the LCQM with experimental observables at HERA and future EIC, providing a comprehensive framework for understanding pion structure through PDFs, structure functions, and cross-sections.

#PionPDFs #LCQM #DGLAP #StructureFunction #DrellYan #EIC #QCD

🚀 Starting a New Research Chapter in Taiwan

I have joined the Academia Sinica as a Research Assistant at the Institute of Physics, working under the supervision of Prof. Wen-Chen Chang.

Research Focus

My work focuses on:

• 🔹 Detector development for the ePIC experiment — specifically the Zero-Degree Calorimeter (ZDC), a key forward detector for the Electron-Ion Collider (EIC) at Brookhaven National Laboratory
• 🔹 Global analysis of pion and kaon Parton Distribution Functions (PDFs) — extending our understanding of the internal structure of light mesons through next-generation QCD fits

Connection to My Research

This aligns closely with my research interests in hadron structure, Transverse Momentum Dependent distributions (TMDs), and Quantum Chromodynamics (QCD), particularly in the context of the upcoming Electron-Ion Collider (EIC).

Looking Ahead

Excited to work at the interface of theory, phenomenology, and experiment — bridging first-principles QCD calculations with cutting-edge detector instrumentation and collider physics.

#ParticlePhysics #HadronPhysics #QCD #EIC #AcademiaSinica #Research

🎓 Final PhD Viva Voce — Successfully Defended!

Thesis Title: Tomography of Light and Heavy Mesons Using Light-Front Dynamics Candidate: Satyajit Puhan Supervisor: Dr. Harleen Dahiya Institution: Dr. B R Ambedkar National Institute of Technology, Jalandhar Date: 2nd April, 2026

Thesis Overview

The thesis presents a comprehensive investigation of the internal structure of light and heavy mesons (pion, kaon, ρ-meson, charmonium, bottomonium) using the Light-Front Quark Model (LFQM). Key contributions include:

• Parton Distribution Functions (PDFs): Leading-twist and subleading-twist PDFs with NLO/NNLO DGLAP evolution
• Transverse Momentum Dependent Distributions (TMDs): Complete sets of leading-twist TMDs including tensor-polarized TMDs for spin-1 mesons
• Generalized Parton Distributions (GPDs): Full extraction of chiral-even and chiral-odd GPDs
• Gravitational Form Factors (GFFs): Mass A(t) and D-term D(t) form factors revealing the mechanical structure of hadrons
• Nuclear Medium Effects: Investigation of meson properties in symmetric nuclear medium at various baryonic densities

Defense Highlights

The defense featured live interactive visualizations built for this research:

• αₛ(Q²) Running Coupling Constant — Interactive 1-loop, 2-loop, and 3-loop pQCD evolution with real-time parameter adjustment
• Pion Mechanical Structure — Visualization of pressure distributions, mass form factors, and D-term form factors in the LFQM

Publications

The thesis work has resulted in 25 publications in leading peer-reviewed journals including Physical Review D, JHEP, Physics Letters B, Nuclear Physics B, PTEP, European Physical Journal, and Chinese Physics C.

With deep gratitude to my supervisor Dr. Harleen Dahiya, my collaborators, and the entire research group at NIT Jalandhar.

Title: Internal Structure of Light Mesons Using the Power Law Wave Function Authors: Satyajit Puhan, Narinder Kumar, Harleen Dahiya Journal: Modern Physics Letters A (MPLA), World Scientific Special Issue Guest Editor: Dr. Parada Hutauruk Accepted: April 1, 2026

Summary

We study the internal structure of the pion and kaon using spin-improved power-law wave functions within the light-front framework. Key results include:

• Distribution Amplitudes (DAs): Leading-twist DAs evolved using LO ERBL equations; pion DA symmetric and consistent with asymptotic result 6x(1−x)
• Generalized Parton Distributions (GPDs): Unpolarized GPDs at zero skewness; pion symmetric, kaon asymmetric due to heavier strange quark
• Transverse Momentum Dependent Distributions (TMDs): Leading-twist unpolarized TMD f₁(x,k⊥²) for both mesons
• Parton Distribution Functions (PDFs): NLO DGLAP evolved to Q² = 16 GeV²; only 41% of longitudinal momentum carried by quarks, with 60% carried by gluons
• Form Factors: Charge form factors in good agreement with NA7, FNAL, and JLab experimental data
• Charge Radii: r_π = 0.668 fm and r_K = 0.704 fm

Decay Constants

• Pion: 114 MeV (PDG: 130.2±1.7 MeV, error: 12.44%)
• Kaon: 144 MeV (PDG: 156.1±0.5 MeV, error: 7.69%)

Congratulations to the team! 🎉 As Dr. Narinder Kumar said — "Gift for Satyajit!!"

The school will be hosted by the Indian Institute of Technology Bombay (IITB) in collaboration with CTEQ Collaboration and the Center for Frontiers in Nuclear Science (CFNS) of Stony Brook University.

The 2026 IITB-CFNS-CTEQ School on Perturbative QCD for EIC will be held 8 to 15 February 2026 at the Indian Institute of Technology Bombay (IITB) in Mumbai, India.

The school is ideally suited for advanced graduate students, postdocs, and junior faculty, with a curriculum that includes a focused introduction to perturbative quantum chromodynamics, along with applications and recent experimental results. It will also offer "hands-on" tutorial sessions on Monte Carlo event generators.

International Organizing Committee: Asmita Mukherjee, V. Ravindran, Abhay Deshpande, Ross Corliss, Huey-Wen Lin, Zack Sullivan, Fred Olness

Local Organising Committee: Asmita Mukherjee, Manibrata Sen, Vikram Rentala, Debojit Sarkar

Speakers:

• Abhay Deshpande (Stony Brook & BNL)
• Asmita Mukherjee (IIT-Bombay)
• Amanda Cooper-Sarkar (Oxford)
• Fred Olness (SMU)
• Tomas Jezo (Muenster)
• Cristian Pisano (U. Cagliari)
• Krishna Kumar (UMass Amherst)
• V. Ravindran (IMSC)
• Padmanath Madanagopalan (IMSC)
• Subir Sarkar (Oxford)
• Nilmani Mathur (TIFR)
• Dave Soper (U. Oregon)
• Anurag Tripathi (IIT-Hyderabad)

Supporting Organizations:

• Center for Frontiers in Nuclear Science, Stony Brook University
• The CTEQ Collaboration
• Institute of Mathematical Sciences (IMSc)
• The Board of Research in Nuclear Sciences (BRNS)
• Southern Methodist University

Title: Valence quark distribution of the rho meson using a light-front quark model
Authors: Satyajit Puhan, Shubham Sharma, Narinder Kumar, Harleen Dahiya
Journal: Physical Review D 113, 036030 (2026)
Published: Feb 27, 2026
DOI: 10.1103/xjkc-l5tr

Abstract: We investigate the partonic structure of the ρ meson, the lightest spin-1 vector meson, within the light-front quark model (LFQM). To explore the sensitivity to model assumptions, we employ two distinct types of spin wave functions in the LFQM. Using light-front helicity wave functions, we derive explicit expressions for the leading-twist and subleading-twist quark parton distribution functions (PDFs), and evolve the leading-twist PDFs to higher scales with next-to-leading order (NLO) Dokshitzer--Gribov--Lipatov--Altarelli--Parisi (DGLAP) evolution. We have also calculated the Mellin moment from the evolved PDFs using a simple neural network frame and compared with available theoretical predictions. Furthermore, we compute the full set of nine leading-twist transverse-momentum-dependent distributions (TMDs) for the valence quark in the ρ meson, including three tensor TMDs that arise from spin-1 tensor polarization of the hadron. Positivity constraints for the PDFs and TMDs are examined within this framework. Our findings highlight the crucial role of tensor polarization in shaping the three-dimensional partonic structure of vector mesons.

VENUE: Ramanujan Lecture Hall, ICTS Bengaluru
DATE: 19 January 2026 to 30 January 2026

ORGANIZERS:

• Rick Sandeepan Gupta (TIFR, Mumbai, India)
• Namit Mahajan (PRL, Ahmedabad, India)
• Tuhin S. Roy (TIFR, Mumbai, India)
• Sudhir Vempati (IISc, Bengaluru, India)

About the Program: The aim of the SATPP is to provide exposure/training to postdoctoral fellows and advanced theoretical particle physics students. The goal is not just to provide details of the spectrum of ideas/mechanisms but also to supply essential technical tools that will allow young researchers to think critically and constructively.

This second edition, "Selected Topics in Effective Field Theories (EFTs)," spanned two weeks. The first week focused on topics of low-energy EFTs and the second week concentrated on high-energy EFTs. EFTs provide systematic ways of "describing" the physics of a scale using only the relevant degrees of freedom, essential for understanding our universe from the TeV scale down to observables involving mesons, baryons, and nuclei.

Program Link:
https://www.icts.res.in/program/satpp2026

Title: Spectroscopy of ρ-meson in symmetric nuclear medium
Authors: Anshu Gautam, Tanisha, Satyajit Puhan, Arvind Kumar, Harleen Dahiya
Date: Jan 16, 2026
e-Print: 2601.11082 [hep-ph]

Abstract (arXiv): In this work, we investigate the behavior of the light vector ρ meson in the presence of a symmetric nuclear medium at zero temperature. We calculate the mass and decay constant of the ρ-meson as well as the leading twist distribution amplitudes (DAs) in the light-front quark model in vacuum, which are further investigated at different baryonic densities. We also predict the Mellin moments of the DAs and decay width of the ρ0 → e+ e- process in both vacuum and medium. The evolution of DAs is carried out by the leading order (LO) Efremov-Radyushkin-Brodsky-Lepage method and compared with available predictions. For better understanding of medium effects on ρ-meson, we have also predicted the in-medium charge (Gc(Q²)), magnetic (Gm(Q²)), and quadrupole (Gq(Q²)) form factors. The in-medium charge radii, magnetic moment, and quadrupole moment have also been predicted in this work. We have found that the nuclear medium induces appreciable modifications on the mass, weak decay constant, decay width, and distribution amplitudes of the ρ meson. However, the charge radii, magnetic moment, and quadrupole moment are observed to exhibit weaker sensitivity to changes in baryonic density.