Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Q18: Minisymposium on Precision Measurements with LeptonsLive Mini-Symposium
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Sponsoring Units: DPF Chair: Bertrand Echenard, Caltech |
Monday, April 19, 2021 10:45AM - 11:09AM Live |
Q18.00001: Theory on BSM Explanations on Flavor Anomalies Invited Speaker: Gino Isidori Recent results in semi-leptonic B-meson decays exhibit interesting hints of discrepancies from the Standard Model predictions. More precisely, data seem to indicate a non-universal behaviour of the different lepton species in such processes. I will show how all the different hints provide a coherent picture, indicating the existence of a new flavor non-universal interaction, i.e. an interaction distinguishing the different fermion families. The implications of these findings for the ultraviolet completion of the Standard Model, and for future searches of new physics both at low- and at high-energies are also briefly discussed. [Preview Abstract] |
Monday, April 19, 2021 11:09AM - 11:21AM Live |
Q18.00002: Prospects of semitauonic measurements at Belle II Invited Speaker: Florian Bernlochner The study of lepton flavor universality violation (LFUV) in semitauonic $b$-hadron decays has become increasingly important in light of longstanding anomalies in their measured branching fractions, and the very large datasets anticipated from the LHC and Belle II. Belle II is a next-generation SuperB-Factory and successfully started its physics run in 2019. It is expected that Belle II will collect a first sizeable data set in 2021. In this talk, I review the expected sensitivity of semitauonic and other relevant auxiliary measurements to probe LFUV at Belle II. Furthermore, I will discuss how property measurements using full differential information will be obtained in the future in an unbiased way, and how such information can be combined with similar measurements from LHCb and across multiple channels. [Preview Abstract] |
Monday, April 19, 2021 11:21AM - 11:45AM Live |
Q18.00003: Electroweak penguin anomalies Invited Speaker: Manuel Franco Sevilla Several LHCb measurements of ratios of $B\rightarrow K^{(*)} \mu^+\mu^-$ and angular distributions in the low dimuon mass region have shown deviations greater than two standard deviations ($\sigma$) from the Standard Model. Currently, the branching fraction for $B_s^0\rightarrow \mu^+\mu^-$ obtained by averaging LHCb, CMS and ATLAS measurements is also 2.1$\sigma$ low, supporting the other results. The current status and updated results from the LHC experiments and the B-factories on ${\cal R}(K)$, ${\cal R}(K^*)$, the dilepton angular distributions, and $B_s^0\rightarrow \mu^+\mu^-$ will be shown. [Preview Abstract] |
Monday, April 19, 2021 11:45AM - 12:09PM Live |
Q18.00004: Lepton flavour violaton in muon decays Invited Speaker: Luca Galli Lepton flavour violation is prohibited in the Standard Model of particle physics, thus its observation would clearly spots out the existence of physics beyond it. The muon sector is the most promising in this field. Muon properties, such as lifetime and mass, enable to construct very high intense and low energy $\mu$-beams to be then transported on a target of a dedicated experimental apparatus and measure the emerging decay products. The lepton flavour violating decays under study are $\mu\rightarrow e\gamma$ and $\mu\rightarrow e e e$; in addition the $\mu$ to e conversion is very promising channel as well. In the intensity frontier physics four experiments are in the commissioning phase aiming at searching for deviations from the Standard Model predictions a in the range $10^{-14} \div 10^{-17}$, depending on the process under study, thanks to innovative detector and beam line technologies. Currently two experiments for the measurement of the $\mu$ to e transitions are in preparation, Mu2e @FNAL and COMET @J-PARC; the MEG II experiment @Paul Scherrer Institut will measure the $\mu\rightarrow e\gamma$ decay and the Mu3e the $\mu\rightarrow eee$ also @PSI. In the talk I will review possible Standard Model extensions from a phenomenological point of view and how future experiments results are complementary to define the nature of new physics, in case any evidence arises. I will show the technological challenges for any of the searches with focus on the recent progresses of the MEG II and Mu3e experiments at the Paul Scherrer Institut. [Preview Abstract] |
Monday, April 19, 2021 12:09PM - 12:33PM Live |
Q18.00005: Recent results from the Muon {\boldmath $g-2$} Experiment at Fermilab Invited Speaker: Anna Driutti At present the most recent experimental measurement of the anomalous magnetic moment of the muon and the Standard Model prediction differ by more than 3 standard deviations, which indicates the possibility of new physics. The Muon $g-2$ Experiment aims to have a final measurement with a precision of 140 parts per billion, which is a four-fold improvement over the previous BNL results. An intense muon beam is circulated inside of a storage ring with a uniform magnetic field. The muon anomaly is measured by precisely determining the muon spin precession frequency, relative to the muon momentum, and the average magnetic field seen by the beam. This talk will discuss the status of the Run-1 data analysis, focusing on the unique experimental challenges presented during this first production run. [Preview Abstract] |
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