1,721,153 research outputs found
Hints of large tanβ in flavour physics
No full textAbstractMotivated by the first evidence of the Bu→τν transition reported by Belle [Belle Collaboration, K. Ikado, et al., hep-ex/0604018] and by the precise ΔMBs measurement by CDF [CDF Collaboration, G. Gomez-Ceballos, Talk presented at FPCP 2006, Vancouver, Canada, 9–12 April 2006, http://fpcp2006.triumf.ca/; D∅ Collaboration, V. Abazov, hep-ex/0603029], we analyse these and other low-energy observables in the framework of the MSSM at large tanβ. We show that for heavy squarks and A terms (Mq˜, AU ≳1 TeV) such scenario has several interesting virtues. It naturally describes: (i) a suppression of B(Bu→τν) of (10–40)%, (ii) a sizable enhancement of (g−2)μ, (iii) a heavy SM-like Higgs (mh0∼120 GeV), (iv) small non-standard effects in ΔMBs and B(B→Xsγ) (in agreement with present observations). The possibilities to find more convincing evidences of such scenario, with improved data on B(Bu→τν), B(Bs,d→ℓ+ℓ−) and other low-energy observables, are briefly discussed
On the breaking of lepton flavor universality in B decays
Get PDFIn view of recent experimental indications of violations of Lepton Flavor Universality (LFU) in B decays, we analyze constraints and implications of LFU interactions, both using an effective theory approach, and an explicit dynamical model. We show that a simple dynamical model based on a SU(2)(L) triplet of massive vector bosons, coupled predominantly to third generation fermions (both quarks and leptons), can significantly improve the description of present data. In particular, the model decreases the tension between data and SM predictions concerning: i) the breaking of tau-mu universality in B --> D-(*())l nu decays; ii) the breaking of mu-e universality in B --> Kl(+)l(-) decays. Indirectly, the model might also decrease the discrepancy between exclusive and inclusive determinations of \V-cb\ and \V-ub\. The minimal version of the model is in tension with ATLAS and CMS direct searches for the new massive vectors (decaying into tau(+)tau(-) pairs), but this tension can be decreased with additional non-standard degrees of freedom. Further predictions of the model both at low- and high-energies, in view of future high-statistics data, are discussed
Probing the Charm Quark Yukawa Coupling in Higgs+Charm Production
No full textWe propose a new method for determining the coupling of the Higgs boson to charm quarks, via Higgs production in association with a charm-tagged jet: pp→hc. As a first estimate, we find that at the LHC with 3000 fb-1, it should be possible to derive a constraint of order one, relative to the standard model (SM) value of the charm Yukawa coupling. As a by-product of this analysis, we present an estimate of the exclusive pp→HD(∗) electroweak cross section. Within the SM, the latter turns out to be not accessible at the LHC even in the high-luminosity phase
Mysteries in Flavour Physics
No full textAbstract:
I will give a general introduction to flavour physics, within and beyond the Standard Model. I will devote particular attention to the concept of Lepton Flavour Universality, and the theoretical description of rare B decays of the type b→s ℓ+ℓ– (ℓ = e, μ).
Bio Gino Isidori:
Gino Isidori is a Professor of Theoretical Physics at the University of Zurich. He graduated at University of Rome La Sapienza in 1991, where he also obtained the PhD in physics in 1996. He has been visiting scientist at SLAC (Stanford), and a CERN Fellow. From 2000 till 2014 he has been a member of INFN Laboratories in Frascati, where he became INFN Research Director in 2018. He has been a Guest Professor at Scuola Normale Superiore in Pisa, in 2017, and at the Technical University of Munich, in 2019. Between 2011 and 2013 he was a scientific associate at CERN. His research activity focus on the theory and phenomenology of fundamental interactions. He provided seminal contributions in the area of Higgs physics and Flavor physics, both within and beyond the Standard Model. His most influential results include the demonstration of the metastability of the Standard Model vacuum, and the formulation of the hypothesis of Minimal Flavor Violation. Since 2015 his research group at the University of Zurich is playing a leading role in the theoretical interpretation of the B-physics anomalies. </p
Mysteries in Flavour Physics
No full textAbstract:
In this lecture I will discuss the theoretical interpretation of the recent anomalies in semileptonic B decays in terms of physics beyond the Standard Model. The results will be analysed in a bottom-up approach, starting from a general Effective Theory analysis and then focusing on a few more ambitious ultraviolet completions of the Standard Model. I will devote particular attention to the predictions of such models for ongoing and future experiments, both in B physics and beyond.
Bio Gino Isidori:
Gino Isidori is a Professor of Theoretical Physics at the University of Zurich. He graduated at University of Rome La Sapienza in 1991, where he also obtained the PhD in physics in 1996. He has been visiting scientist at SLAC (Stanford), and a CERN Fellow. From 2000 till 2014 he has been a member of INFN Laboratories in Frascati, where he became INFN Research Director in 2018. He has been a Guest Professor at Scuola Normale Superiore in Pisa, in 2017, and at the Technical University of Munich, in 2019. Between 2011 and 2013 he was a scientific associate at CERN. His research activity focus on the theory and phenomenology of fundamental interactions. He provided seminal contributions in the area of Higgs physics and Flavor physics, both within and beyond the Standard Model. His most influential results include the demonstration of the metastability of the Standard Model vacuum, and the formulation of the hypothesis of Minimal Flavor Violation. Since 2015 his research group at the University of Zurich is playing a leading role in the theoretical interpretation of the B-physics anomalies.
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B-physics anomalies : a guide to combined explanations
Get PDFMotivated by additional experimental hints of Lepton Flavour Universality violation in B decays, both in charged- and in neutral-current processes, we analyse the ingredients necessary to provide a combined description of these phenomena. By means of an Effective Field Theory (EFT) approach, based on the hypothesis of New Physics coupled predominantly to the third generation of left-handed quarks and leptons, we show how this is possible. We demonstrate, in particular, how to solve the problems posed by electroweak precision tests and direct searches with a rather natural choice of model parameters, within the context of a flavour symmetry. We further exemplify the general EFT findings by means of simplified models with explicit mediators in the TeV range: coloured scalar or vector leptoquarks and colour-less vectors. Among these, the case of an -singlet vector leptoquark emerges as a particularly simple and successful framework
Stability of the electroweak ground state in the Standard Model and its extensions
Get PDFWe review the formalism by which the tunnelling probability of an unstable ground state can be computed in quantum field theory, with special reference to the Standard Model of electroweak interactions. We describe in some detail the approximations implicitly adopted in such calculation. Particular attention is devoted to the role of scale invariance, and to the different implications of scale-invariance violations due to quantum effects and possible new degrees of freedom. We show that new interactions characterized by a new energy scale, close to the Planck mass, do not invalidate the main conclusions about the stability of the Standard Model ground state derived in absence of such terms
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