scholarly journals Flavoured axions in the tail of Bq → μ+μ− and B → γ* form factors

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Johannes Albrecht ◽  
Emmanuel Stamou ◽  
Robert Ziegler ◽  
Roman Zwicky
Keyword(s):  
Sum Rules ◽  
Form Factors ◽  
Resonance Region ◽  
Decay Rates ◽  
Beyond The Standard Model ◽  
Background Process ◽  
Full Generality ◽  
Shell Form ◽  
The Standard Model ◽  
First Time

Abstract We discuss how LHC di-muon data collected to study Bq → μμ can be used to constrain light particles with flavour-violating couplings to b-quarks. Focussing on the case of a flavoured QCD axion, a, we compute the decay rates for Bq → μμa and the SM background process Bq → μμγ near the kinematic endpoint. These rates depend on non-perturbative Bq → γ(*) form factors with on- or off-shell photons. The off-shell form factors — relevant for generic searches for beyond-the-SM particles — are discussed in full generality and computed with QCD sum rules for the first time. This includes an extension to the low-lying resonance region using a multiple subtracted dispersion relation. With these results, we analyse available LHCb data to obtain the sensitivity on Bq → μμa at present and future runs. We find that the full LHCb dataset alone will allow to probe axion-coupling scales of the order of 106 GeV for both b → d and b → s transitions. As a spin-off application of the off-shell form factors we further analyse the case of light, Beyond the Standard Model, vectors.

scholarly journals A puzzle in $$\varvec{\bar{B}_{(s)}^0 \rightarrow D_{(s)}^{(*)+} \lbrace \pi ^-, K^-\rbrace }$$ decays and extraction of the $$\varvec{f_s/f_d}$$ fragmentation fraction

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Marzia Bordone ◽  
Nico Gubernari ◽  
Tobias Huber ◽  
Martin Jung ◽  
Danny van Dyk
Keyword(s):  
Form Factors ◽  
Hadronic Decay ◽  
Hadronic Decays ◽  
Beyond The Standard Model ◽  
Qcd Factorization ◽  
Substantial Discrepancy ◽  
Quantitative Estimates ◽  
The Standard Model ◽  
The Matrix ◽  
First Time

AbstractWe provide updated predictions for the hadronic decays $$\bar{B}_s^0\rightarrow D_s^{(*)+} \pi ^-$$ B ¯ s 0 → D s ( ∗ ) + π - and $$\bar{B}^0\rightarrow D^{(*)+} K^-$$ B ¯ 0 → D ( ∗ ) + K - . They are based on $${\mathcal {O}}(\alpha _s^2)$$ O ( α s 2 ) results for the QCD factorization amplitudes at leading power and on recent results for the $$\bar{B}_{(s)} \rightarrow D_{(s)}^{(*)}$$ B ¯ ( s ) → D ( s ) ( ∗ ) form factors up to order $$\mathcal{O}(\Lambda _\mathrm{QCD}^2/m_c^2)$$ O ( Λ QCD 2 / m c 2 ) in the heavy-quark expansion. We give quantitative estimates of the matrix elements entering the hadronic decay amplitudes at order $$\mathcal{O}(\Lambda _\mathrm{QCD}/m_b)$$ O ( Λ QCD / m b ) for the first time. Our results are very precise, and uncover a substantial discrepancy between the theory predictions and the experimental measurements. We explore two possibilities for this discrepancy: non-factorizable contributions larger than predicted by the QCD factorization power counting, and contributions beyond the Standard Model. We determine the $$f_s/f_d$$ f s / f d fragmentation fraction for the CDF, D0 and LHCb experiments for both scenarios.

scholarly journals Beyond $$M_{t\bar{t}}$$: learning to search for a broad $$t\bar{t}$$ resonance at the LHC

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Sunghoon Jung ◽  
Dongsub Lee ◽  
Ke-Pan Xie
Keyword(s):  
Invariant Mass ◽  
Common Knowledge ◽  
Resonance Region ◽  
Invariant Mass Spectrum ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Angular Correlations ◽  
Additional Information ◽  
The Standard Model ◽  
Learning Technique

Abstract A resonance peak in the invariant mass spectrum has been the main feature of a particle at collider experiments. However, broad resonances not exhibiting such a sharp peak are generically predicted in new physics models beyond the Standard Model. Without a peak, how do we discover a broad resonance at colliders? We use machine learning technique to explore answers beyond common knowledge. We learn that, by applying deep neural network to the case of a $$t\bar{t}$$tt¯ resonance, the invariant mass $$M_{t\bar{t}}$$Mtt¯ is still useful, but additional information from off-resonance region, angular correlations, $$p_T$$pT, and top jet mass are also significantly important. As a result, the improved LHC sensitivities do not depend strongly on the width. The results may also imply that the additional information can be used to improve narrow-resonance searches too. Further, we also detail how we assess machine-learned information.

scholarly journals A global view of the off-shell Higgs portal

2020 ◽  
Vol 8 (2) ◽  
Author(s):  
Maximilian Ruhdorfer ◽  
Ennio Salvioni ◽  
Andreas Weiler
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Vector Boson ◽  
Effective Interaction ◽  
Goldstone Boson ◽  
High Energy ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Higgs Portal ◽  
First Time

We study for the first time the collider reach on the derivative Higgs portal, the leading effective interaction that couples a pseudo Nambu-Goldstone boson (pNGB) scalar Dark Matter to the Standard Model. We focus on Dark Matter pair production through an off-shell Higgs boson, which is analyzed in the vector boson fusion channel. A variety of future high-energy lepton colliders as well as hadron colliders are considered, including CLIC, a muon collider, the High-Luminosity and High-Energy versions of the LHC, and FCC-hh. Implications on the parameter space of pNGB Dark Matter are discussed. In addition, we give improved and extended results for the collider reach on the marginal Higgs portal, under the assumption that the new scalars escape the detector, as motivated by a variety of beyond the Standard Model scenarios.

scholarly journals Detailed study of the Λb → Λcτν̄τ decay

2018 ◽  
Vol 33 (29) ◽  
pp. 1850169 ◽  
Author(s):  
E. Di Salvo ◽  
F. Fontanelli ◽  
Z. J. Ajaltouni
Keyword(s):  
Standard Model ◽  
Semileptonic Decay ◽  
Form Factors ◽  
Higgs Doublet ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Left Handed ◽  
The Standard Model ◽  
Analogous Formula ◽  
Two Higgs Doublet Model

We examine in detail the semileptonic decay [Formula: see text], which may confirm previous hints, from the analogous [Formula: see text] decay, of a new physics beyond the Standard Model. First of all, starting from rather general assumptions, we predict the partial width of the decay. Then we analyze the effects of five possible new physics interactions, adopting in each case five different form factors. In particular, for each term beyond the Standard Model, we find some constraints on the strength and phase of the coupling, which we combine with those found by other authors in analyzing the analogous semileptonic decays of [Formula: see text]. Our analysis involves some dimensionless quantities, substantially independent of the form factor, but which, owing to the constraints, turn out to be strongly sensitive to the kind of nonstandard interaction. We also introduce a criterion thanks to which one can discriminate among the various new physics terms: the left-handed current and the two-Higgs-doublet model appear privileged, with a neat preference for the former interaction. Finally, we suggest a differential observable that could, in principle, help to distinguish between the two cases.

scholarly journals Status of Charm Flavor Physics

2006 ◽  
Vol 21 (27) ◽  
pp. 5381-5403 ◽  
Author(s):  
Ian Shipsey
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Flavor Physics ◽  
Form Factors ◽  
New Physics ◽  
Model Description ◽  
Beyond The Standard Model ◽  
Physics Program ◽  
The Standard Model ◽  
The Status

The role of charm in testing the Standard Model description of quark mixing and CP violation through measurements of lifetimes, decay constants and semileptonic form factors is reviewed. Together with Lattice QCD, charm has the potential this decade to maximize the sensitivity of the entire flavor physics program to new physics and pave the way for understanding physics beyond the Standard Model at the LHC in the coming decade. The status of indirect searches for physics beyond the Standard Model through charm mixing, CP-violation and rare decays is also reported.

Hypergeometric representation of one-loop Higgs decay to two photons

2019 ◽  
Vol 97 (10) ◽  
pp. 1096-1103 ◽  
Author(s):  
Khiem Hong Phan
Keyword(s):  
Standard Model ◽  
Hypergeometric Function ◽  
Form Factors ◽  
Space Time ◽  
Time Dimension ◽  
Function Representation ◽  
Higgs Decay ◽  
The Standard Model ◽  
Arbitrary Space ◽  
First Time

In this paper, we derive hypergeometric function representation of one-loop contributing to Higgs decay to two photons in the standard model and its extensions. The calculations are performed at general space–time dimension d. For the first time, analytic results are published for form factors that are valid in arbitrary space–time dimension. Moreover, we confirm against analytic results in previous computations that have been available in space–time dimension d = 4 – 2ϵ at ϵ0 expansions.

Why Antimatter Matters

2015 ◽  
Vol 23 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Alban Kellerbauer
Keyword(s):  
Large Hadron Collider ◽  
Discrete Symmetries ◽  
Particle Physics ◽  
Hadron Collider ◽  
Beyond The Standard Model ◽  
Parity Symmetry ◽  
The Standard Model ◽  
Charge Parity ◽  
First Time ◽  
The Universe

Almost ten years after the first production of cold antimatter at CERN, the confinement of antihydrogen has recently been achieved for the first time. Several experiments installed at the Antiproton Decelerator intend to test the symmetry between matter and antimatter by means of trapped anti-atoms. In addition, in the coming years it is planned to study the effect of gravity on antiparticles for the first time. Meanwhile, evidence from the Large Hadron Collider hinting at a violation of charge–parity symmetry beyond the Standard Model of particle physics has yet to be confirmed. A violation of the discrete symmetries that describe the relation between matter and antimatter could explain the excess of ordinary matter in the Universe.

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