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## Aktualności

# Blogi

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, April 16 at 12:15, which will be given by

Roman Skibiński (IF UJ)

entitled

„Towards relativistic description of reactions in two- and three-nucleon systems ".

Abstract:

Two- and three-nucleon systems are an important field of study of nuclear interactions. In such systems, it is possible to study both strong interactions, e.g. in the process of elastic proton-deuteron scattering, and electroweak processes, e.g. in the scattering of neutrinos on deuteron. The starting point for this research is a specific model of nucleon-nucleon interaction. In recent years, the previously used non-relativistic formalism has been extended to include some elements of relativistic dynamics, which allows for an increase in the reaction energy and eliminates one of the sources of uncertainty in the study of two- and three-nucleon potentials. The most important elements of that relativistic approach, selected results obtained so far and plans for further development of this approach will be discussed.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Friday, April 5 at 13:00, which will be given by

Stefan Hoche (Fermilab)

entitled

„Precision simulations of light and heavy jets".

Abstract:

I will introduce a new parton shower algorithm for the numerical resummation of large logarithms in perturbative QCD. It is based on a novel matching of the classical radiation pattern to the collinear limit, combined with a recoil scheme that satisfies the criteria for next-to-leading logarithmic precision. I will also present an extension of the method to heavy quark evolution and introduce a Monte-Carlo method to implement heavy quark production in a variable flavor number scheme. First applications of the parton shower to the Drell-Yan transverse momentum spectrum, and of the variable flavor number scheme to the fully differential simulation of ttbb will be discussed.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, March 26 at 12:15, which will be given by

Indaco Biazzo (Polytechnique de Lausanne)

entitled

„Boltzmann Autoregressive Neural Networks".

Abstract:

Generative Autoregressive Neural Networks (ARNNs) excel in generative tasks across various domains, including images, language, and science. Particularly in physics, they have successfully applied to generate samples from statistical physics models. Despite their success, ARNN architectures often operate as black boxes without a clear connection to underlying physics or statistical models. This seminar explores the direct link between neural network architectures and physics models. I'll show how the neural network parameters align with Hamiltonian couplings and external fields, highlighting the emergence of residual connections and recurrent architectures from the derivation. By leveraging statistical physics techniques, we formulate ARNNs for specific systems, and I’ll discuss a new approach for sampling from sparse interacting systems, crucial for physics, optimization, and inference problems. Our findings validate a physically informed approach and suggest potential extensions to multi-valued variables, paving the way for broader applications in scientific research.

References:

[1] Biazzo, Indaco. "The autoregressive neural network architecture of the Boltzmann distribution of pairwise interacting spins systems." Communications Physics 6.1 (2023): 296.

[2] Biazzo, Indaco, Dian Wu, and Giuseppe Carleo. "Sparse Autoregressive Neural Networks for Classical Spin Systems." arXiv preprint arXiv:2402.16579 (2024).

The speaker will be on-line, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, March 19 at 12:30, which will be given by

Paul Caucal (SUBATECH UMR 6457 (IMT Atlantique, Universite de Nantes, IN2P3/CNRS))

entitled

„SIDIS at next-to-leading order in the Regge limit".

Abstract:

The theoretical search for "golden channels" to measure gluon saturation in high-energy hadronic collisions is an active area of research given the arrival of the Electron Ion Collider. Recently, it has been shown that very forward single jet or hadron production in the Regge limit of semi-inclusive DIS could be a promising observable to reveal non-linear saturation effects in large nuclei [1].

In this talk, I will discuss this observable beyond leading order in pQCD at small-x. Within the Color Glass Condensate (CGC) effective field theory, we have computed in [2] the next-to-leading order (NLO) cross-section for the single-jet semi-inclusive cross-section in deep inelastic scattering (DIS) at small-x. Our analytic expressions, valid at finite Nc and suitable for numerical evaluation, demonstrate that the very forward rapidity regime is plagued by large double logarithmic corrections coming from phase space constraints on soft gluons close to the kinematic threshold for jet production. A joint resummation of small-x and threshold logarithms is proposed to remedy the instability of the cross-section in the very forward jet limit. Finally, I will comment on the phenomenological consequences of QCD radiative corrections in the search for saturation signatures in SIDIS, as well as on-going progresses in the numerical evaluation of the full NLO cross-section.

Refs:

[1] Iancu, Mueller, Triantafyllopoulos, Wei, JHEP 07 (2021) 196,

[2] Caucal, Ferrand, Salazar, arXiv:2401.01934

The speaker will be on-line, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, March 12 at 12:15, which will be given by

Alexander Korchin

(Jagiellonian University & Kharkiv Institute of Physics

and Technology & V.N. Karazin Kharkiv National University, Ukraine)

entitled

„Search for effects beyond the Standard Model in some decays of the Higgs boson".

Abstract:

Effects of possible CP violation in the Higgs-boson decays to (i) two photons, (ii) photon and Z boson, (iii) photon and a pair of leptons, are studied with a particular emphasis on polarization effects. We also discuss a hypothetical non-Hermiticity of the Yukawa interaction of the Higgs boson with fermions. The influence of the non-Hermiticity on the Higgs decay to a pair of polarized tau leptons is investigated. The longitudinal polarization of tau lepton is shown to be a direct measure of the CP violation and non-Hermiticity of the Yukawa interaction. The contributions to the longitudinal polarization of leptons and quarks that arise due to the loop corrections with the Hermitian interaction are also evaluated.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, March 5 at 12:15, which will be given by

Nikodem Witkowski (IFT UJ)

entitled

„Deuteron production in a combined thermal and coalescence framework for heavy-ion collisions in the few-GeV energy regime".

Abstract:

A recently formulated thermal model for hadron production in heavy-ion collisions in the few-GeV energy regime is combined with the idea that some part of protons and neutrons present in the original thermal system forms deuterons via the coalescence mechanism. Using realistic parametrizations of the freeze-out conditions, which reproduce well the spectra of protons and pions, we make predictions for deuteron transverse-momentum and rapidity spectra. The best agreement with the experimentally known deuteron yield is obtained if the freeze-out temperature is relatively high and, accordingly, the system size at freeze-out is rather small. In addition, the standard Gaussian distribution of the relative distance between nucleons is replaced by the distribution resulting from their independent and approximately uniform production inside the initial thermal system.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, February 27 at 12:15, which will be given by

Samapan Bhadury (IFT UJ)

entitled

„Intertwined chiral restoration and spin polarization".

Abstract:

The physics of the recently observed spin polarization of hadrons in heavy-ion collisions is still ambiguous and is under intense investigation. The evolution of the medium is governed by QCD. Thus, it is necessary to incorporate the equation of state (EoS) for the hot QCD medium in our theory. This can be achieved by considering an effective model with a spacetime-dependent mass. Hence, we start from the semiclassical expansion of the Wigner function for spin-1/2 particles, whose kinetic equation is obtained from the NJL model. We find the gradient of the effective mass can be interpreted as a source of the spin polarization. This is also consistent with the conservation of total angular momentum. While, under the simple boost-invariant dynamics the effective mass depends only on proper time and consequently decouples from the dynamics of spin, an extension to non-boost invariant expansion, shows a non-trivial connection between the spin polarization and chiral restoration.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Z wielkim żalem przyjęliśmy wiadomość, że 30 stycznia 2024 roku zmarł w

Syracuse, USA Wojciech Furmański, jeden z najbardziej rozpoznawalnych fizyków teoretyków związanych z Instytutem Fizyki UJ. W pierwszych latach kariery naukowej, na początku lat siedemdziesiątych, pracował pod kierunkiem

profesora Romualda Wita zajmując się własnościami amplitud rozpraszania

pionów. W tym okresie zainteresował się modelem partonów Feynmana i

procesami produkcji cząstek z dużym pędem poprzecznym, do których można

było stosować metody właśnie w tym czasie sformułowanej chromodynamiki

kwantowej. Wówczas rozpoczął badania nad udowodnieniem w ramach

chromodynamiki kwantowej faktoryzacji w kanale s, w szczególności w

procesach 𝑒+𝑒−.

Prace Furmańskiego zostały natychmiast rozpoznane w świecie i

zaowocowały, jeszcze w Krakowie, intensywną współpracą z Roberto Petronzio z

CERNu. Trwała ona dalej podczas pobytu Wojtka w Genewie. Furmański wraz z

Petronzio wykonali obliczenia poprawek logarytmicznych do modelu partonów i

w roku 1980 wspólnie z C. Curcim opublikowali artykuł, w którym udowodnili

faktoryzację w rozpraszaniu 𝑒𝑝 i 𝑒+𝑒− przy dużych przekazach pędu. Wynik ten

miał fundamentalne znaczenie dla rozwoju perturbacyjnej chromodynamiki

kwantowej i jest do dzisiaj cytowany w literaturze ponad 1500 razy.

W latach 80. zainteresowania Furmańskiego nieco się zmieniły i podjął on

badania nad zjawiskiem uwięzienia kwarków, które prowadzi się przy użyciu

symulacji komputerowych. W tym czasie przebywał, już na zaproszenie Richarda

Feynmana, w CALTECH'u. Wojtek wraz Geofreyem Foxem rozwijali nowoczesne

metody obliczeniowe, byli pionierami w dziedzinie sieci neuronowych. Założyli

firmę komputerową zajmującą się oprogramowaniem na procesory równoległe.

Zainteresowania technikami obliczeniowymi spowodowały, że Furmański podjął

pracę w centrum superkomputerowym na Uniwersytecie Nowego Jorku w

Syracuse. Był zaangażowany w prace nad oprogramowaniem dla akceleratora

SSC (Superconducting Super Collider), wielokanałową komunikacją

bezprzewodową oraz sztuczną inteligencją. Ostatecznie Wojtek Furmański

związał się z Boeingiem, gdzie pracował do końca życia.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, January 23 at 12:15, which will be given by

Francesco Giuli (ATLAS, CERN)

entitled

„High-precision measurements of Z-boson p_T and a_S with ATLAS".

Abstract:

In this seminar, I will present a measurement of the production properties of the Z boson in the full phase space of the decay leptons at 8 TeV with the ATLAS detector, and a very precise determination of the strong-coupling constant from the same dataset.

The speaker will be on-line, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, January 16 at 12:15, which will be given by

Michał Iglicki (Chalmers University of Technology)

entitled

„In-medium regularization of t-channel singularities of scattering processes".

Abstract:

Let us consider a 2-2 scattering process described by a t-channel diagram. If the mediator (the intermediate t-channel state) is kinematically allowed to be on mass-shell (p^2 = m^2), the matrix element suffers from a singularity caused by vanishing denominator of the Feynman propagator. It is then impossible to calculate the reaction rate, making it hard to obtain any quantitative predictions of, e.g., a given model of beyond-SM physics. Usually, to cure this issue, one uses the resummed propagator instead of the bare one. Then, the mediator's decay width provides a non-zero imaginary contribution to the denominator of the on-shell propagator, regularizing the singularity. Even if the mediator is stable (which is often the case in processes involving hypothetical dark particles), it can acquire an effective decay width due to interactions with particles forming the environment (medium) of the process. In such a case, the above method can still be employed. In my talk, I will provide a strict set of conditions for a given process to be affected by the singularty. I will also present and discuss results for the medium-induced effective width calculated for mediator of spin 0, 1/2 or 1. The discussion will be illustrated with examples coming from analysis of the so-called vector-fermion dark matter model.

(based on DOI:10.1007/JHEP06(2023)006, 10.1016/j.nuclphysb.2022.115967)

The speaker will be on-line, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, December 19 at 12:15, which will be given by

Aleksander Kusina (IFJ PAN)

entitled

„Short range correlations and high-x structure of nuclei".

Abstract:

The structure of nucleons as well as nuclei at large longitudinal momenta, x, is crucial for understanding QCD confinement or for explaining the origins of the nuclear EMC effect. Parton distribution functions (PDFs), which describe the longitudinal structure of hadrons or nuclei, are typically determined in global analysis of experimental data. Unfortunately, the high-x region is hard to determine due to different theoretical effects that enter in this challenging region. In this talk I present a recent analysis where we have accounted for them and determined nuclear PDFs using high-x data from JLAB experiments. I also present preliminary results of a related study where such analysis was preformed in a framework inspired by short-range correlation (SRC) models which are used to explain nuclear EMC effect. It showed remarkable agreement with the traditional purely phenomenological fitting framework as well as some low energy data and nuclear calculations.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Piotr Korcyl, Jacek Wosiek, Michał Praszałowicz

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, December 12 at 12:15, which will be given by

Dimitri Colferai (Universita di Firenze and INFN Firenze)

entitled

„Small-x resummation of photon impact factors and virtual photon scattering at high energies".

Abstract:

After a brief introduction on the peculiarities of QCD in the high-energy regime and the BFKL approach for its description, we proceed to the theoretical analysis of virtual photon scattering. Here, the crucial theoretical objects are the photon impact factors and the BFKL gluon Green's function, which up to now are known in leading and next-to-leading logarithmic approximation. We improve the theoretical description of the virtual photon cross section by performing the renormalization group improved collinear resummation of impact factors and Green's function. Our analysis is consistent with previous impact factor calculations at NLO, apart from a new term proportional to CF that we find for the longitudinal polarization. Finally, we use the resummed cross section to compare with the LEP data and with previous calculations. The resummed result is lower than the leading logarithmic approximation but higher than the pure next-to-leading one, and is consistent with the experimental data.

Based on arXiv: hep-ph 2311.07443.

The speaker will be remote, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, December 5 at 12:15, which will be given by

Rene Poncelet (IFJ PAN)

entitled

„ Precision phenomenology with heavy-flavour jets at the LHC".

Abstract:

Jets are a staple of the research program at high-energy hadron colliders. As suitably defined sets of highly-energetic particles, they constitute a useful tool to establish a link between Quantum Chromodynamics (QCD) of quarks and gluons and the realm of actual strongly-interacting particles, baryons and mesons. Besides the general importance of jets for collider phenomenology, there is a growing interest in studying jet substructure in order to disentangle various QCD effects governing jet dynamics. Final states with jets identified to originate from heavy quarks play a vital role, for example, in understanding the process of heavy-quark fragmentation and the contents of protons at high energy. In this talk I will discuss fixed-order NNLO QCD phenomenology, comparisons thereof to data and infrared-safe flavoured jet algorithms, a non-trivial ingredient in defining useful collider observables.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, November 28 at 12:15, which will be given by

Pan Kessel (Genentech Roche)

entitled

„Generative Model for Sampling in Theoretical Physics".

Abstract:

An important problem that arises throughout theoretical physics is the following: given an unnormalized distribution (or energy), we want to sample from this distribution. Various Monte-Carlo algorithms exist to facilitate sampling with asymptotic guarantees. However, they can suffer from slow mixing and large autocorrelation. In this talk, I will give a brief introduction to deep generative models and discuss why they have the potential to considerably speed up such sampling problems. I will also discuss the open challenges with this approach. I will mainly focus on lattice field theory applications for illustration.

The speaker will be on-line, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, November 21 at 12:15, which will be given by

Sanjin Benić (University of Zagreb)

entitled

„ Odderon at the EIC from exclusive production of C-even charmonia".

Abstact:

Recently, TOTEM and D0 collaborations announced the discovery of the odderon in the pp vs ppbar elastic cross section difference [1,2]. Our main goal here is to investigate the potential for the odderon detection at the future EIC. This talk is focused on our recent computation [3,4] of exclusive C-even charmonia productions in high-energy electron-proton collisions. The C-even charmonia states serve as a probe of the odderon amplitude in the proton which is an off-forward generalized transverse momentum distribution formed by at least three gluons in a C-odd state. The computation is based on the Color Glass Condensate framework, where we numerically solve the Balitsky- Kovchegov evolution equation for coupled pomeron-odderon system. Our initial conditions are based on a microscopic quark model computation [5] that is an essential ingredient for a proper account of the so-called Donnachie-Landshoff mechanism according to which even a large-|t| scattering would not break up the proton if it involves a three-gluon exchange. Our comprehensive results cover the exclusive production of the eta_c meson [4] and the chi_cJ family (J = 0, 1, 2) [3]. While eta_c was originally suggested already long time ago [6], chi_c was not discussed so far. Due to the large branching ratio to J\Psi+gamma we argue that chi_c should be a more suitable channel for the potential odderon detection at the EIC. In our computation we pay special attention to the interference with the Primakoff process where our model computation fixes the relative phase between the two contributions. We demonstrate how the deviations from the purely Primakoff contribution can be used as a probe of the odderon amplitude in the proton at the EIC.

[1] TOTEM collaboration, Eur. Phys. J. C 80, 91 (2020) [2] D0 collaboration, Phys. Rev. D 86, 012009 (2012) [3] SB, A. Dumitru, A. Kaushik, L. Motyka, T. Stebel, in preparation [4] SB, D. Horvatic, A. Kaushik, E. A. Vivoda, Phys. Rev. D 108 (2023) 7, 074005 [5] A. Dumitru, H. Mantysaari, R. Paatelainen, Phys. Rev. D 107, L011501 (2023) [6] J. Czyzewski, J. Kwiecinski, L. Motyka, and M. Sadzikowski, Phys. Lett. B 398, 400 (1997)

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, November 14 at 12:15, which will be given by

Farid Taghinavaz (School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran)

entitled

„Relativistic hydrodynamics with phase transitions".

Abstact:

It has been confirmed by many observations that the Quark-Gluon plasma is a new type of matter that is produced after the collisions of heavy ions and in today’s energies it behaves like (almost) perfect fluid. The relativistic hydrodynamics (RH) is an appropriate tool to describe the dynamics of this complicated system near the local equilibrium or even far from equilibrium. However, there has been several unsolved issues by using the RH which one of them is how to employ it or in what extent the RH is valid near the phase transition points. We benefit of the gauge/gravity duality to study the time-dependent perturbations of the dual metric in a short-wave-length limit at a certain phenomenological model, the so called Einstein-Klein-Gordon model. We will examine the radius of convergence of the hydro series near the critical points for various kinds of phase transitions as well as different spin-sectors.

The speaker will be on-site, local participants are invited to meet in the seminar room D-2-02.

Piotr Korcyl, Jacek Wosiek, Michał Praszałowicz

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, November 7 at 12:15, which will be given by

Maxim Nefedov (Universite Paris-Saclay, CNRS)

entitled

„ Curing high-energy instability of quarkonium production cross sections with High-Energy Factorisation".

The speaker will be online, local participants are invited to meet in the seminar room D-2-02.

Dear All,

We have the pleasure to invite you to the Particle Theory Seminar on Tuesday, October 24 at 12:15, which will be given by

James Whitehead (IFJ PAN)

entitled

„The KrkNLO method for NLO parton shower matching".

Abstract:

'Matched' calculations combining the next-to-leading-order (NLO) accuracy of perturbative QCD with the logarithmic resummation of a parton shower are a key workhorse driving LHC phenomenology in the precision era. The KrkNLO method for NLO parton shower matching uses multiplicative reweighting and a convenient choice of PDF factorisation scheme to produce matched NLO + parton shower predictions. By construction, it guarantees positive weights. I will present an introduction to the theory of NLO matching, an overview of the KrkNLO method, and phenomenological results from the implementation of new processes in Herwig 7.

The seminar will be in in-person mode in the seminar room D-2-02, but you can also attend remotely through Zoom.

Piotr Korcyl, Jacek Wosiek, Michał Praszałowicz

Dear All,

We have the pleasure to invite you to the Particle Theory Seminar on Tuesday, October 17 at 12:15, which will be given by

Yizhuang Liu (IFT UJ)

entitled

„ A survey of the heavy-light Sudakov universality class".

The seminar will be in in-person mode in the seminar room D-2-02, but you can also attend remotely through Zoom:

Piotr Korcyl, Jacek Wosiek, Michał Praszałowicz

Dear All,

We have the pleasure to invite you to the Particle Theory Seminar (together with the Field Theory Department) on Tuesday, October 10 at 14:00 (different time!), which will be given by

Błażej Ruba (University of Copenhagen)

entitled

„Dense and strongly interacting nonrelativistic fermions".

Abstract:

I will discuss estimates of the ground state energy of interacting nonrelativistic fermions obtained using an approximate bosonization method. The new result concerns the strongly coupled regime, which I will compare to the perturbative regime and the critical scaling conventionally called "mean field".

The seminar will be in in-person mode in the seminar room D-2-02, but you can also attend remotely through Zoom:

Piotr Korcyl, Jacek Wosiek, Michał Praszałowicz