Project

Flavour Physics; Particle Physics; CP violation; Rare B decays; LHC; LHCb

Lead
I decadimenti adronici con "beauty" e semileptonici rari sono fra i campi più promettenti per la ricerca di estensioni del Modello Standard, indicate anche come "Nuova Fisica". Nel mio progetto propongo dei nuovi metodi per confermare, in maniera indipendente e complementare, le anomalie osservate dalla collaborazione LHCb nel settore della fisica del "flavour" e fornisco delle misure ausiliari che permetteranno di ridurre le incertezze teoriche ora presenti.
Lay summary
2. Piano di ricerca Recenti studi dei decadimenti semileptonici rari dei mesoni con "beauty" mostrano delle interessanti discrepanze  con il Modello Standard (MS). Malgrado la significatività di tali risultati non risulti essere ancora conclusiva,  è fondamentale utilizzare dei nuovi approcci per confermare  indipendentemente le attuali anomalie. In questo progetto mi prefiggo di attuare delle nuove misure che permetteranno di rivelare senza ambiguità la natura delle anomalie del "flavour". La ricerca di violazione CP nei decadimenti dei barioni  con "beauty" è diventato sperimentalmente accessibile solo di recente in LHCb. Questo fenomeno è legato all'asimmetria materia-antimateria nell'universo e la sua osservazione nel settore barionico aprirebbe un nuovo campo di esplorazione nel MS. Grazie ai dati raccolti da LHCb nel primo e secondo run del LHC, studierò i canali più sensibili per questo effetto con un grande potenziale di scoperta. 3.Contesto scientifico e sociale Il progetto  si propone di trovare delle prove a conferma dell'esistenza di nuovi fenomeni nella fisica dei quark con "flavour" o di porre dei limiti stringenti sul loro effetto nel MS. Questi risultati chiariranno il comportamento della Nuova Fisica e potrebbero pertanto rivoluzionare l'attuale comprensione  delle interazioni fisiche a breve distanza.

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Last update: 24.08.2017

Lead
Rare semileptonic and hadronic beauty decays provide some of the most promising framework to search for extensions of the Standard Model of particle physics, also referred to as "New Physics". In my project, I propose novel approaches to independently and complementary confirm the present anomalies observed by the LHCb collaboration in the flavour physics sector and, provide crucial auxiliary measurements which will allow to reduce the existing theoretical uncertainties.
Lay summary
2. Research plan Recent studies of rare semileptonic decays of beauty mesons reported some intriguing discrepancies with the Standard Model (SM). Whilst the level of significance of these results are not conclusive yet, novel approaches to independently and complementary confirm the present anomalies are paramount. In this research I will pursuit new measurements that can reveal unambiguously the existence of New Physics (NP) and the nature of these flavour anomalies. Searches for CP violation in decays of beauty baryons became experimentally accessible only recently with LHCb. This phenomenon is related to the matter-antimatter asymmetry of the Universe, and its observation in the baryonic sector would open a new field of exploration and provide new probes for the SM. With the unprecedented LHCb dataset collected in the first and second runs of the LHC, I aim to study the most sensitive channel for this effect with a great discovery potential.  3. Scientific and societal context I expect with this research to either find evidence for new phenomena in quark flavour physics, or to place stringent bounds on the size of any NP effects. These results will yield insight as to how NP behaves, and could therefore revolutionise our understanding of physics interaction at the smallest distances.

Direct link to Lay Summary

Last update: 24.08.2017

Active participation

Communication	Title	Media	Place	Year

The discovery of the long-awaited Higgs boson at the Large Hadron Collider (LHC) confirms the remarkable success of the Standard Model (SM) of particle physics. While in the last decades high-energy experiments have verified to an impressive level of accuracy the predictions of the SM, the theory is not complete, and it does not provide explanations for dark matter, neutrino oscillation or the baryogenesis. A number of extensions of the SM have been proposed (e.g. the existence of new massive particles), and direct searches for New Physics (NP) effects are currently the dominant experimental effort of the particle physics community. Since not clear sign of NP has been seen, indirect searches, which are highly sensitive to new particles effects at higher scales and new couplings, are becoming of crucial importance. In particular, stringent constraints in the phase space of NP contributions have been placed in a series of important observables. A prime example is the heavy flavour physics programme that studies interactions that differ among flavours, mainly in decays involving c and b quarks. This term has been firstly introduced by Murray Gell-Mann and his student, when noting that "just as ice-cream has both colour and flavour so do quarks" (and leptons). In the SM, flavour-physics refers to the weak and Yukawa interactions, and NP could introduce additional flavoured interactions. There are two main motivations for ongoing experimental investigations into this field: search for rare or SM forbidden processes beyond the current energy frontier; and CP violation and its connection to the matter-antimatter asymmetry of the Universe. My proposed project aims to improve the understanding of rare semileptonic and hadronic b-hadron decays, by addressing both of the aforementioned key measurements: flavour anomalies in b -> s l+ l- transitions that could be a genuine sign of NP and CP violation in b baryons. Recent studies of rare semileptonic decays of beauty mesons, mediated through virtual quantum loops, reported some intriguing discrepancies with the SM predictions, which seems to form a coherent pattern. In particular, in the angular observables P'5 of the B0 -> K*0 mu+ mu- decay and the suppression of the muon channel in the ratio of branching fractions of B+ -> K+ mu+ mu- to B+ -> K+ e+ e- transitions. In order to achieve a conclusive understanding of these anomalies, a close collaboration between theory and experiment, with novel approaches that include all of the information that is relevant for the theory calculations is paramount. The proposed research will, for the first time, disentangle hadronic long-distance effects from NP contributions, that currently limit the unambiguous claim of existence of physics beyond the SM. In addition, the nature of the flavour anomalies, mainly its connection with the hypothesis that particles couple unequally to different flavours of leptons, will be finally completely elucidated. Searches for CP violation in decays of beauty baryons to purely hadronic final states became experimentally accessible only recently with the start of LHCb. First asymmetry measurements in multi-body charmless decays have been carried out by me and no significant CP violation has been observed. More recently, a first evidence of this phenomena in Lb -> p pi- pi+ pi- has been reported by LHCb. This has an extraordinary impact to the field and further measurements with other multi-body beauty baryon decays are compulsory to confirm such observation. In this project, the golden channel Lb -> p K*- is studied in a Dalitz-plot analysis of the decay Lb -> K0 p pi-. This has a great potential to make the first observation of CP violation in b baryons and also provide deeper insights on the dynamics of these processes. Ultimately, I expect with this research to either find evidence for new phenomena in quark flavour physics, or to place stringent bounds on the size of any NP effects, using the unprecedented LHCb dataset available in Run-I and II. Regardless of the outcome, my results will yield insight as to how NP behaves, and could therefore revolutionise our understanding of physics interaction at the smallest distances.