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Flavour: a portal to discover new physics

Applicant Serra Nicola
Number 182622
Funding scheme Project funding (Div. I-III)
Research institution Physik-Institut Universität Zürich
Institution of higher education University of Zurich - ZH
Main discipline Particle Physics
Start/End 01.04.2019 - 31.03.2021
Approved amount 458'463.00
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Keywords (5)

LHCb; Lepton Flavour Universality; Data Analysis; Particle Physics; Flavour Phyisics

Lay Summary (Italian)

Lead
L'interazione microscopica tra particelle elementari è descritta dal così detto Modello Standard (MS). Il MS descrive con un'impressionante precisione interazioni e decadimenti di particelle. Tuttavia, il modello non spiega alcune osservazioni di natura Cosmologica o Astrofisica, come l'esistenza della Materia Oscura, oppure il fatto che il nostro Universo sia dominato da materia (piuttosto che antimateria). Per queste ragioni, la ricerca di evidenze microscopiche di particelle e/o forze non presenti nel MS è uno dei principali filoni di ricerca in fisica delle particelle. Qui propongo di cercare tali evidenze sperimentali investigando le così dette anomalie del "sapore".
Lay summary
La materia è composta da quarks (costituenti di protoni e neutroni) e leptoni (come ad esempio l'elettrone). Sia quarks che leptoni compaiono in tre famiglie o sapori. Il MS predice che le tre famiglie di leptoni abbiano un comportamento identico rispetto alle tre forze del MS (elettromagnetica, forte e debole). Questa proprietà è nota come Universalità Leptonica. 
Recentemente, l'esperimento LHCb al CERN di Ginevra ha misurato delle anomalie che sembrano suggerire alterazioni dall'Universalità Leptonica. Tali anomalie, note come anomalie del sapore, consistono in deviazioni rispetto alle predizioni del MS per le probabilità relative di decadimento di alcune particelle.
Se le anomalie del sapore fossero confermate,  costituirebbero la prima evidenza sperimentale diretta di fisica oltre il MS, ed aprirebbero la strada per comprendere varie questioni che il MS non riesce spiegare. 
La mia ricerca si propone di eseguire misure fondamentali per determinare se tali anomalie siano o meno dovute a fluttuazioni statistiche ovvero errori strumentali, oppure siano genuini segnali di fisica oltre il MS.   
Direct link to Lay Summary Last update: 13.12.2018

Responsible applicant and co-applicants

Employees

Publications

Publication
Angular Analysis of the B+→K*+μ+μ− Decay
Aaij R., Beteta C. Abellán, Ackernley T., Adeva B., Adinolfi M., Afsharnia H., Aidala C. A., Aiola S., Ajaltouni Z., Akar S., Albrecht J., Alessio F., Alexander M., Albero A. Alfonso, Aliouche Z., Alkhazov G., Cartelle P. Alvarez, Amato S., Amhis Y., An L., Anderlini L., Andreianov A., Andreotti M., Archilli F., et al. (2021), Angular Analysis of the B+→K*+μ+μ− Decay, in Physical Review Letters, 126(16), 161802-161802.
Hunting for $$B^+\rightarrow K^+ \tau ^+\tau ^-$$ imprints on the $$B^+ \rightarrow K^+ \mu ^+\mu ^-$$ dimuon spectrum
Cornella C., Isidori G., König M., Liechti S., Owen P., Serra N. (2020), Hunting for $$B^+\rightarrow K^+ \tau ^+\tau ^-$$ imprints on the $$B^+ \rightarrow K^+ \mu ^+\mu ^-$$ dimuon spectrum, in The European Physical Journal C, 80(12), 1095-1095.
zfit: scalable pythonic fitting
Eschle Jonas, Navarro Puig Albert, Silva Coutinho Rafael, Serra Nicola (2020), zfit: scalable pythonic fitting, in EPJ Web of Conferences, 245, 06025-06025.
zfit: scalable pythonic fitting
EschleJonas, AlbertPuig Navarro, RafaelSilva Coutinho, NicolaSerra (2020), zfit: scalable pythonic fitting, in SoftwareX, 11, 100508.
Probing effects of new physics in $$ {\varLambda}_b^0\to {\varLambda}_c^{+}{\mu}^{-}{\overline{v}}_{\mu } $$ decays
Ferrillo Martina, Mathad Abhijit, Owen Patrick, Serra Nicola (2019), Probing effects of new physics in $$ {\varLambda}_b^0\to {\varLambda}_c^{+}{\mu}^{-}{\overline{v}}_{\mu } $$ decays, in Journal of High Energy Physics, 2019(12), 148-148.
Simulating the LHCb hadron calorimeter with generative adversarial networks
LancieriniDavide (2019), Simulating the LHCb hadron calorimeter with generative adversarial networks, in Simulating the LHCb hadron calorimeter with generative adversarial networks, Nuovo Cimento, C 42 (2019) 4, 197.

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Ein Experiment am Cern rüttelt an den Grundfesten der Physik – allerdings nur sanft NZZ German-speaking Switzerland 2021
Media relations: print media, online media Interview mit Cern-Forscher-«Es wäre die grösste Entdeckung seit Jahrzehnten» Tages Anzeiger German-speaking Switzerland 2021
Media relations: print media, online media Nicola Serra: Der Jäger der fünften Kraft Higgs.ch German-speaking Switzerland 2021

Associated projects

Number Title Start Funding scheme
204238 Understanding the Flavour Anomalies 01.10.2021 Project funding (Div. I-III)
173104 What's behind Flavour Anomalies? 01.07.2017 SNSF Professorships

Abstract

While the Standard Model of Particle Physics is incomplete and cannot explain phenomena such as the existence of Dark Matter and the large asymmetry between matter and anti-matter in the Universe, we still do not have a clear microscopic evidence of physics Beyond the Standard Model (BSM). Therefore, searches for New Physics effects are currently the dominant experimental effort of the particle physics community, in particular for the LHC experiments ATLAS, CMS and LHCb. While direct searches at general purpose experiments (ATLAS and CMS) are probing unprecedented energy scales (e.g. putting the most stringent constraints on low energy SUSY), no clear sign of New Physics has been seen. The situation is different in flavour physics, where an interesting pattern of deviations from SM expectations seems to be emerging. These Flavour Anomalies consist of measurements of the ratios of branching ratios R(D(*)) = B(B->D(*)tau nu)/B(B->D(*)mu nu) in semileptonic B-meson decays; and measurements of rare decays in LHCb, such as the ratio of branching ratios R(K(*)) and angular observables in the decay B -> K0*µ+µ-. While the statistical significance of each of these anomalies is not large enough to be considered a discovery of New Physics, they all together significantly deviate from the Standard Model. Intriguingly, these anomalies form a coherent pattern, that seems to reveal a hierarchical structure in the flavour of quarks and leptons, which might be the key to shed light into the flavour puzzle.Here I describe a set of measurements that can be performed with the large dataset that have been collected by LHCb in Run2 and that will allow to unambiguously determine if flavour anomalies are a genuine sign of BSM physics. I expect with my research to either find evidence for new phenomena or to place stringent bounds on the size of any New Physics effects.
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