Month: Marzec 2023

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