Time-Reversal Symmetry and Geometric Constraints on the Residue Phase of Pion Photoproduction via Δ(1232)

Ceci, S.; Omerović, R.; Osmanović, H.; Uroić, M.; Vukšić, M.; Zauner, B. Time-Reversal Symmetry and Geometric Constraints on the Residue Phase of Pion Photoproduction via Δ(1232). 

Symmetry 2026, 18, 1184. 

https://doi.org/10.3390/sym18071184

The electromagnetic coupling phase at the complex resonance pole is a fundamental property of nucleon excitations. However, its extraction from pion photoproduction data remains model-dependent, particularly for the 𝛥(1232)  resonance, where modern multichannel analyses report helicity amplitude phases ranging from +3 to −18°. In this Letter, we present a largely model-independent geometric S-matrix formalism that provides a physical constraint for this ambiguity. By imposing Watson’s final-state interaction theorem, a direct consequence of S-matrix unitarity and time-reversal symmetry, on the real energy axis and performing an analytic continuation, we isolate the kinematic threshold barriers of the photoproduction (𝑘·𝑞) and elastic (𝑞3) amplitudes. For the dominant 𝑀1+ multipole transition of the 𝛥(1232), our method yields a kinematically constrained prediction of 𝜙𝐸𝑀=−8.5°+0.6°−1.0° for the electromagnetic residue phase. This geometric constraint explains the numerical results of coupled-channel phenomenological fits, validating the extractions by the SAID and Bonn–Gatchina groups, and establishes a theoretical benchmark for evaluating resonance properties.

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Geometric Constraint on Residue Phases: Resolving the N (2190) Anomaly and Implications for Exotic States

S. Ceci, R. Omerović, H. Osmanović, M. Uroić, M. Vukšić, B. Zauner, Geometric constraint on residue phases: resolving the N(2190) anomaly and implications for exotic states, Physics Letters B, Volume 875, 2026, 140332, ISSN 0370-2693, https://doi.org/10.1016/j.physletb.2026.140332.

(https://www.sciencedirect.com/science/article/pii/S0370269326001863)

Abstract: We derive a parameter-free geometric constraint on residue phases dictated by the pole-threshold angle. Using the N(2190) anomaly as a test case, this constraint reveals a sign ambiguity in prior data; correcting the sign ambiguity yields a phase of −28∘±10∘, matching our prediction. This consistency validates the method as a model-independent diagnostic for distinguishing compact from molecular states, offering a rigorous tool for exotic spectroscopy.

Keywords: Unitary S-matrix; Baryon and meson resonances; Resonant properties

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No hidden physics in resonance pole residue phase

New publication: 

S. Ceci, R. Omerović, H. Osmanović, M. Uroić, B. Zauner, No hidden physics in resonance pole residue phase, Physics Letters B, 2025, 140136, ISSN 0370-2693,
https://doi.org/10.1016/j.physletb.2025.140136
(https://www.sciencedirect.com/science/article/pii/S0370269325008925)

 
Abstract: In hadron resonant scattering, there are four fundamental resonant parameters: real and imaginary parts of the pole position, and the magnitude and the phase of the residue. Out of the four, the last one is the least understood. The search for the residue phase’s physical meaning has focused on model-independent phases of the majority of the lowest-mass resonances. Here, we apply a simple mathematical identity to the amplitude in the complex plane to reveal the exact reason for the noticed regularity and show that there is no room for hidden physical variables in the residue phase.
Keywords: Resonant scattering; Unitary S-matrix; Resonant properties; Baryon and meson resonances

 

 

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ANU BiH: Susreti mladih istraživača BiH iz STEM oblasti

 Susreti mladih istraživača Bosne i Hercegovine iz oblasti prirodnih, tehničkih i matematičkih nauka (STEM) održani su 3. i 4. novembra 2023. godine u organizaciji Odjeljenja tehničkih nauka Akademije nauka i umjetnosti Bosne i Hercegovine i u saradnji s Federalnim ministarstvom obrazovanja i nauke.

Jedan od glavnih ciljeva ovog skupa bio je uspostavljanje kontakata s mladim istraživačima porijeklom iz Bosne i Hercegovine koji djeluju u STEM oblastima na univerzitetima i istraživačkim institucijama u svijetu.

Skup je prvenstveno bio namijenjen studentima doktorskih studija u STEM oblastima i mladim istraživačima koji su doktorirali u posljednjih pet godina, ali i svim zainteresiranim istraživačima, članovima akademske i naučne zajednice u Bosni i Hercegovini te predstavnicima bh. privrede.

Skup se sastojao iz tri dijela: dva pozivna predavanja koja su održali gospodin Namik Hrle, inostrani član ANUBiH, IBM Fellow, direktor IBM-ovih globalnih razvojnih timova iz područja baza podataka i umjetne inteligencije i direktor IBM-ove najveće razvojne laboratorije u Njemačkoj i Suad Krilašević, doktorand na Tehničkom univerzitetu u Delftu i predsjednik Asocijacije za napredak nauke i tehnologije u Bosni i Hercegovini.

U drugom dijelu skupa predstavljeno je 28 prezentacija istraživanja studenata III ciklusa i mladih istraživača koji su doktorirali u proteklih 5 godina. Naučni odbor skupa dodijelio novčane nagrade za najbolje prezentacije istraživanja.

Detaljnije na LINKU!

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KLF Collaboration

At the first stage the KLF (K Long Facility) program will focus on two-body and quasi-two-body reactions: elastic $K_L p → KS_p$ and charge-exchange $K_L p → K^+ n$ reactions, then on two-body reactions producing $S = −1$ ($S = −2$) hyperons as $K_L p → π + \Lambda$, $K_L p → \pi+Σ^0$ , and $K_L p → π^0 \Sigma^+ (K_L p → K+Ξ 0 )$, as well as three body $K_L p → K^+ K^+ \Omega^ −$.

A coupled channel PWA of the KLF data can be performed standalone and in conjunction with an analysis of the data from the J-PARC K−p measurements, if available. The best fit will determine the partial wave amplitudes and the resonance pole positions, residues and Breit-Wigner (BW) parameters. These will provide a benchmark for results of forthcoming Lattice QCD calculations and elucidate the structure of the strange hyperons.

PWA Tuzla Group is a part of the KLF Collaboration.

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STRONG 2020 Workshop

 

STRONG 2020 (14-16 September - University of York) is included in the activities of the working package WP25 (Light-and heavy-quark hadron spectroscopy) of the project STRONG-2020. It has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824093.

POSTER: SE  PWA for pion photoproduction with vfixed-t analyticity

The major topics of the workshop will cover:

1) Precision calculations in non-perturbative QCD: Effective Field Theories, analyticity, dispersion relations and Lattice QCD

2) Spectroscopy & Exotic states

3) Hadron Decays & Production

4) Form factors, LECs, fundamental parameters of QCD and light nuclei
spectroscopy

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