Author: Wojciech Orpel

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 2 czerwca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Tau neutrinos. What do we know? What can we learn from them?”

Referuje: dr hab. Katarzyna Grzelak (IFD UW)

Tau neutrinos are the least studied leptons. Due to difficulty in distinguishing tau neutrinos from other neutrino flavours, low cross-section and high threshold energy for charged-current interactions only 19 tau neutrino candidates have been event-by-event selected to date.

In the seminar the current status of tau neutrino-related physics, new experiments and new ideas to improve our knowledge of lepton sector will be presented.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERG

Dnia 26 maja (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Gravitational wave astrophysics at the beginning of O4”

Referuje: prof. dr hab. Tomasz Bulik (OA UW)

Abstract

The O4 observational run is starting now. I will review the current
detections and their significance for astronomy and fundamental physics.
As the bulk of detections are binary black holes I will describe the
currently considered models of their formation and compare
the predictions of these models with the data.
Finally I will talk about hopes for the O4 run

.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 19 maja (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Towards identifying the sources of Ultra-High Energy Cosmic Rays with the GRAND experiment”

Referuje: dr Lech Wiktor Piotrowski (IFD)

Even though the first UHECR was detected almost 60 years ago, the origin of these particles remains a mystery. For lower energies, their paths are twisted by the Galactic magnetic field, while for higher energies their fluxes are extremely low. That makes identifying the sources unreachable even for the largest existing observatories, that occupy hundreds to thousands of square kilometres.

The problem of the low flux can be solved with building observatories that observe orders of magnitude larger volume of the atmosphere than the current ones. In addition, looking not directly at UHECR, but at neutrinos generated by them close to the source, can eliminate the influence of cosmic magnetic fields. These two ideas will be incorporated into the Giant Radio Array for Neutrino Detection (GRAND) – a future experiment to detect Earth-skimming neutrinos with huge arrays of cheap radio antennas.

The contents of the seminar will include the idea behind the radio detection of UHE CRs and neutrinos, current status of GRAND prototypes, the role of the Polish group and the experimental challenges that we are facing.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 28 kwietnia (piątek) o godzinie 10:15, odbędzie się seminarium online, na którym zostanie wygłoszony referat pt.:

„Study of neutrino mass ordering with the atmospheric neutrinos at Super-Kamiokande”

Referuje: dr Magdalena Posiadała-Zezula (IFD)

Super-Kamiokande (Super-K) is the world’s largest underground water Cherenkov detector which has been studying the atmospheric neutrino oscillations since 1996. Atmospheric neutrinos are famous for covering a wide energy range, have both neutrinos and antineutrinos, with electron and muon flavours, which oscillate to tau neutrinos and are sensitive for matter effects in the earth. Analysis of the atmospheric neutrino data from all five run periods of Super-K running with ultra-pure water, years 1996 – 2020, will be presented. The fiducial volume region has been expanded from 22,5 kton to 27,2 kton, which allowed us to use also the events with reconstructed vertex at least 1~m from the nearest wall of the detector. Additional studies have been performed by adding information from T2K published binned data muon neutrino disappearance and electron appearance. Over the range of parameters allowed at 90% confidence level, the normal mass ordering for neutrinos  is favoured based on the combined results from Super-K and with T2K results.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 21 kwietnia (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Strange phase in beautiful oscillation: Measurement of weak phase  in the neutral bottom meson decay”

Referuje: dr Alibordi Muhammad (IFD)

The smallest deviation from the precise value of the CP-violating weak phase predicted by Standard Model  in the B_s to Jpsiphi decay mode would hint for a new domain of physics. Also improving precision with higher statistics of the Run-II proton-proton collision data collected by CMS detector may help to constrain the future theories. These were the motivations of measuring the weak phase in the B_s to Jpsiphi decay.

In this talk we will see how the weak phase measurement is done with ~97fb^-1 of the 13TeV proton-proton collision data and what level of precision is achieved.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 31 marca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Measurements of CP-violating asymmetries in charm decays in the charmingly-beauty experiment – LHCb”

Referuje: dr hab. Artur Ukleja (NCBJ), prof. AGH

mgr Jakub Ryżka (AGH)

One the main goal of High Energy Physics is a search for physics beyond the Standard Model (called new physics). The measurements of CP-violating asymmetries in particle decays containing a charm quark create perfect environment for the new physics searches since the background from the Standard Model is small as the expected value of CP violation is about a few per milles or less. It is significantly smaller then observed in beauty sector. The LHCb experiment tests the Standard Model predictions in very precise measurements of CP violation using very sophisticated research methods. For example, finding disagreement between measured and predicted values will be indirect indication of the existence of new physics.

So far, in the charm sector, CP violation is confirmed as a nonzero difference between two CP-violating asymmetries in D^0 to K^- K^+ and D^0 to pi^- pi^+ decays. This result obtained in 2019 only raised the question of whether the observed difference reflects the CP violation in the D0 meson decays into a pair of kaons, into a pair of pions, or both. Possible interpretations will be discussed during the seminar. Recently, the LHCb experiment has measured the direct CP asymmetries separately for the two decay modes: D^0 to K^- K^+ and D^0 to pi^- pi^+. These results will be presented during the seminar as them constitute the first evidence for CP violation in a specific charm hadron decay. The compatibility with the hypothesis of CP symmetry is 3.8 standard deviations.

The new searches for CP asymmetries in three-body charm baryon decays will be also presented. Three-body processes are always more rare than the two-body processes, but they can provide much more information about CP violation. Many observables are available to measure in multi-body processes. In contrast, in two-body processes, only one variable is measured (global result of CP violation). So far, in charm baryons the level of 2.7 standard deviations of agreement with CP symmetry was measured. The new approaches will be discussed during seminar as well as their tests obtaining in control decays.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 24 marca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Searching for dark matter with liquid-argon detectors”

Referuje: dr. Marek Walczak (AstroCeNT / CAMK PAN)

The nature of dark matter remains unknown and its origin is currently one of the most important questions in physics. In particular direct searches for WIMP dark matter particle interactions with ordinary matter are carried out with large detectors located in underground laboratories to suppress the background of cosmic rays. One of the currently most promising detection technologies is based on the use of a large mass of liquid argon or xenon as a target in the detector.

In this talk, I will discuss the status and plans for dark matter searches with detectors based on liquid argon. I will present the currently operating DEAP-3600 experiment (at SNOLAB, Canada) and introduce the DarkSide-20k detector (under construction at the Gran Sasso laboratory, Italy) and in particular the design of its neutron veto.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 17 marca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Theoretical motivations and experimental signals for a second resonance of the Higgs field”

Referuje: prof. Maurizio Consoli, INFN, Sezione di Catania, Italy

Theoretical arguments and lattice simulations suggest that, beside the known resonance of mass m_h= 125 GeV, defined by its quadratic shape, the effective potential of the Higgs field could exhibit a second, much heavier mass scale M_H = 690 +/- 30 GeV associated with the zero-point energy which determines its depth. In spite of its large mass, however, the heavier state would couple to longitudinal W’s with the same typical strength as the low-mass state at 125 GeV and thus represent a relatively narrow resonance mainly produced at LHC by gluon-gluon fusion. After summarizing the general aspects, I will consider 4 samples of LHC data (2 from ATLAS and 2 from CMS) which suggest a new resonance with a combined mass value of 691(10) GeV. Since the considered measurements have a negligible correlation and since, when comparing with a definite theoretical prediction, local excesses are not downgraded by the so called look-elsewhere effect, the cumulated statistical significance is now substantial. The issue of the second resonance could thus definitely be settled by just adding one or two crucial, missing samples of RUN2 data.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 10 marca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„LHC searches beyond simplified models”

Referuje: dr hab. Krzysztof Rolbiecki (IFT UW)

In this talk I will discuss a concept of simplified models which is used for interpretation of searches for new physics at the LHC. I will discuss limitations of this approach and the need for reinterpretation of results. Then I will introduce several computer programs that are used to reinterpret ATLAS and CMS searches beyond Standard Model physics. Finally I will show recent examples of reinterpretation efforts from the theory community.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki

SEMINARIUM FIZYKI WIELKICH ENERGII

Dnia 3 marca (piątek) o godzinie 10:15, w sali B2.38 odbędzie się seminarium, na którym zostanie wygłoszony referat pt.:

„Warsaw Active-Target Time Projection Chamber – a powerful tool to study nuclear reactions of astrophysical interests but not only”

Referuje: dr inż. Magdalena Kuich (IFD UW)

Crucial interests in nuclear astrophysics are (p,γ) and (α,γ) reactions. In particular, those that regulate the ratio of C and O and those that burn 18O and, therefore, regulate the ratio between 16O and 18O in the Universe. Such reactions in the stars happen at energies well below the Coulomb barrier and the respective cross-sections are incredibly small, often below the experimental reach. Therefore, the available experimental results on cross-sections for low energies are very sparse, and theoretical extrapolations are burdened with large uncertainties.           

An opportunity to elude a part of the experimental limitations is to study the time-reversal reaction, i.e. photo-disintegration. For this purpose, a novel active-target Time Projection Chamber (TPC) optimised for experiments with high-intensity γ-ray beams was developed and built at the Faculty of Physics, University of Warsaw.

Several experiments with the Warsaw active-target TPC were performed in the summer of 2021 at the IFJ PAN Cracow and in the spring and summer of 2022 at HIgS, TUNL, USA.

Preliminary results of the performed measurements at IFJ and HigS will be presented and an outlook on future experiments will be given.

Serdecznie zapraszamy

dr hab. Katarzyna Grzelak
prof. dr hab. Jan Królikowski
prof. dr hab. Aleksander Filip Żarnecki