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## Aktualności

# Blogi

Dear All,

We have the pleasure of inviting you to the Particle Theory Seminar on Tuesday, June 11 at 12:15, which will be given by

Herve Dutrieux (William & Mary University, Wiliamsburg, USA)

entitled

“Perturbation theory and the calculation of parton distributions on the lattice".

Abstract:

I will present how the perturbative matching used to relate space-like non-local matrix element computed on the lattice to parton distributions is inconvenient due to the low typical scale of the calculations. I will discuss our control of power corrections and lattice artifacts in a recent generalized parton distribution calculation and argue that, once those are under control, alternatives to the simple perturbative matching can be considered.

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, June 4 at 12:15, which will be given by

Jarosław Duda (WMiI UJ)

entitled

“Geometric interpretation of the Standard Model with topological excitations".

Abstract:

In perturbative QFT we decompose scenario into Feynman diagrams, each of them should correspond to a field configuration - I would like to present and discuss geometric/topological approach to find them, based on liquid crystal Landau-de Gennes model from arXiv:2108.07896. To enforce charge quantization in Gauss law, we interpret dual F tensor as curvature of a deeper field (Faber’s approach), this way Gauss law counts its topological charge. Singularity in its center would have infinite energy, we use Higgs-like potential to regularize it to a finite energy, what leads to short range corrections of Coulomb interaction, in agreement with the running coupling effect (arXiv:2210.13374). Living in 3D, charges appear in 3 families of different mass, resembling 3 leptons. There are also 3 types of vortices resembling color strings - which inward/outward field rotation by pi would correspond to elementary electric (as topological) charge, and fractional rotations to 6 types of quarks, e.g. appearing in quark-antiquark pairs with increased energy between them for confinement. The u quark is preferred energetically due to suggested baryon configuration, explaining why proton is lighter than neutron, also e.g. binding mechanism and electric quadrupole moment of deuteron. Hadronization can be viewed here through reconnections of such high energy color string into various final configurations. Neutrino oscillations also seem in agreement: mainly between muon and taon neutrino, with more freedom in PMNS than CKM mixing matrices.

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, May 28 at 12:15, which will be given by

Florian Cougoulic (University of Santiago de Compostella)

entitled

“Cold nuclear effects on azimuthal decorrelation in heavy-ion collisions".

Abstract:

We propose to study hard processes and bulk nuclear matter on the same footing in heavy-ion collisions using Glauber modelling of heavy nuclei. To exemplify this approach, we calculate the leading-order corrections to azimuthal decorrelation in Drell-Yan and boson-jet processes due to cold nuclear effects. At leading order in both the hard momentum scale and the nuclear size, the impact-parameter dependent cross section is found to factorize for both processes. The factorization formula involves a convolution of the hard cross section with the medium-modified initial state parton distributions, and, for the boson-jet production, the medium-modified jet function.

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, May 14 at 12:15, which will be given by

Jamal Jalilian-Marian (Baruch College, City University of New York & Narodowe Centrum Badań Jądrowych)

entitled

„ Deep Inelastic Scattering at small Bjorken x: gluon saturation".

Abstract:

After a brief introduction to the phenomenon of gluon saturation in high energy QCD we consider its signatures in particle production in high energy collisions. In particular we focus on precision studies of gluon saturation in the proposed Electron-Ion Collider and the recent efforts in calculating next to leading order corrections to single and double inclusive hadron production in DIS at small x.

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, May 7 at 12:15, which will be given by

Soham Banerjee (NICER)

entitled

„Longitudinal spin polarization in a thermal model with dissipative corrections".

Abstract:

In this work we address the problem of longitudinal spin polarization of the Lambda hyperons produced in relativistic heavy-ion collisions. We combine a relativistic kinetic-theory framework that includes spin degrees of freedom treated in a classical way with the freeze-out parametrization used in previous investigations. The use of the kinetic theory allows us to incorporate dissipative corrections (due to the thermal shear and gradients of thermal vorticity) into the Pauli-Lubanski vector that determines spin polarization and can be directly compared with the experimental data. As in earlier similar studies, it turns out that a successful description of data can only be achieved with additional assumptions -- in our case they involve the use of projected thermal vorticity and a suitably adjusted time for spin relaxation. The latter turns out to be of about 2--3 fm/c which is compatible with other estimates.

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

Dear All,

We would like to invite you to the EIC PL Seminar on April 22nd (Monday) at 3pm:

https://events.ncbj.gov.pl/e/EICPL

Speaker: Elke-Caroline Aschenauer (Brookhaven National Lab)

Title: The electron-ion collider: A collider to unravel the mysteries of visible matter

Abstract:

Understanding the properties of nuclear matter and its emergence through the underlying partonic structure and dynamics of quarks and gluons requires a new experimental facility in hadronic physics known as the Electron-Ion Collider (EIC). The EIC will address some of the most profound questions concerning the emergence of nuclear properties by precisely imaging gluons and quarks inside protons and nuclei such as their distributions in space and momentum, their role in building the nucleon spin and the properties of gluons in nuclei at high energies. The polarised EIC beams do not only allow to study the longitudinal and transverse polarized nucleon spin structure, but also to use polarization as a vehicle to access nucleon/nuclei structure difficult to study with unpolarized beams. This presentation will give highlights on the EIC science program, introduce the needed experimental equipment and describe the components of the EIC accelerator critical for the science program. The talk will end summarizing the status of the EIC project.

Please remember to send this info to interested people in your Institutions. Thank you.

Best Regards,

Krzysztof Kutak, Jakub Wagner

(on behalf of the representatives, https://eicpl.ifj.edu.pl)

Dear All,

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

Asaad Daher (IFJ PAN)

entitled

„Stability and causality in spin hydrodynamics".

Abstract:

Motivated by the evidence of spin polarisation of particles (Lambda, Xi, and Omega) produced in relativistic heavy ion collisions at various collision energies, there is a growing interest in describing the dynamics of relativistic fluid for particles with spin such as the Quark Gluon Plasma. This talk will briefly introduce one of the possible theoretical approaches known as “spin hydrodynamics” and then discuss its mathematical stability and its causality.

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, 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.