A GLANCE BEYOND THE STANDARD MODEL: LATEST RESULTS FROM THE MEG EXPERIMENT

2014 ◽  
Vol 35 ◽  
pp. 1460390
Author(s):  
SIMEONE DUSSONI
Keyword(s):  
Beyond Standard Model ◽  
Standard Model ◽  
High Intensity ◽  
State Of The Art ◽  
Branching Ratio ◽  
Beyond The Standard Model ◽  
Upper Limit ◽  
The Standard Model ◽  
Key Features ◽  
Very High

The MEG experiment started taking data in 2009 looking for the Standard Model suppressed decay μ → e + γ, which, if observed, can reveal Beyond Standard Model physics. It makes use of state-of-the art detectors optimized for operating in conditions of very high intensity, rejecting as much background as possible. The data taking ended August 2013 and an upgrade R&D is started to push the experimental sensitivity. The present upper limit on the decay Branching Ratio (BR) is presented, obtained with the subset of data from 2009 to 2011 run, together with a description of the key features of the upgraded detector.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

scholarly journals $K_L\to\gamma\nu\bar\nu$ DECAY BEYOND THE STANDARD MODEL

2003 ◽  
Vol 18 (14) ◽  
pp. 977-982 ◽  
Author(s):  
JI-HAO JIANG ◽  
DAO-NENG GAO ◽  
MU-LIN YAN
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
Beyond The Standard Model ◽  
Upper Limit ◽  
The Standard Model

The decay [Formula: see text] is investigated beyond the standard model. Interestingly, the upper limit of the CP-conserving and CP-violating branching ratios of the decay, induced from the possible extensions of the standard model, would be larger than the corresponding branching ratios given in the standard model respectively, and it is expected that the CP-violating part could be enhanced.

scholarly journals An investigation of the very rare $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ decay

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Single Event ◽  
Data Set ◽  
Upper Limit ◽  
The Standard Model

Abstract The NA62 experiment reports an investigation of the $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ K + → π + ν ν ¯ mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ K + → π + ν ν ¯ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of ($$ {0.48}_{-0.48}^{+0.72} $$ 0.48 − 0.48 + 0.72 ) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

POSITRONIUM PHYSICS BEYOND THE STANDARD MODEL

2002 ◽  
Vol 17 (26) ◽  
pp. 1713-1724 ◽  
Author(s):  
S. N. GNINENKO ◽  
N. V. KRASNIKOV ◽  
A. RUBBIA
Keyword(s):  
Standard Model ◽  
Decay Rate ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Additional Dimension ◽  
Upper Limit ◽  
The Standard Model ◽  
Invisible Decays ◽  
Near Future ◽  
Invisible Decay

Possible manifestations of new physics in rare (exotic) decays of orthopositronium (o - Ps) are briefly reviewed. It is pointed out that models with infinite additional dimension(s) of Randall–Sundrum type predict disappearance of orthopositronium into additional dimension(s). The experimental signature of this effect is the invisible decay of orthopositronium. We point out that this process may occur at a rate within two or three orders of magnitude of the present experimental upper limit. We also propose a model with a light weakly interacting boson leading to o - Ps → invisible decays at the experimentally interesting rate. We discuss this in details and stress that the existence of invisible decay of orthopositronium in vacuum could explain the o - Ps decay rate puzzle. Thus, our result enhances the existing motivation and justifies efforts for a more sensitive search for o - Ps → invisible decay in a near future experiment.

scholarly journals Dielectron pairs from η meson decays at WASA detector

2019 ◽  
Vol 199 ◽  
pp. 02011 ◽  
Author(s):  
D. Pszczel ◽  
J. Stepaniak
Keyword(s):  
Transition Form Factor ◽  
Extraction Procedure ◽  
Branching Ratio ◽  
Beyond The Standard Model ◽  
Transition Form ◽  
Proton Proton ◽  
Proton Collisions ◽  
Upper Limit ◽  
The Standard Model ◽  
Proton Proton Collisions

We present the results of the analysis of η → e+e−γ and η → e+e− decays. The experimental data were collected in proton-proton collisions at incident proton kinetic energy 1.4 GeV using the WASA detector and the COSY storage ring. We describe the extraction procedure of the η meson transition form factor, based on a sample of around 108 η mesons, and show an attempt to search for physics beyond the Standard Model that led to the setting of an upper limit on the coupling between photons and hypothetical dark bosons. We also provide an estimate of the branching ratio upper limit for the very rare η → e+e− decay.

scholarly journals EFFECT OF BOTH Z AND Z′ MEDIATED FLAVOR-CHANGING NEUTRAL CURRENTS ON THE BARYONIC RARE DECAY Λb→Λℓ+ℓ-

2009 ◽  
Vol 24 (32) ◽  
pp. 6223-6235 ◽  
Author(s):  
S. SAHOO ◽  
C. K. DAS ◽  
L. MAHARANA
Keyword(s):  
Standard Model ◽  
Z Boson ◽  
Rare Decay ◽  
Branching Ratio ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Neutral Currents ◽  
Flavor Changing ◽  
The Standard Model ◽  
Flavor Changing Neutral Currents

We study the effect of both Z and Z′ mediated flavor-changing neutral currents (FCNCs) on the Λb→Λℓ+ℓ-(ℓ = μ, τ) rare decay. We find the branching ratio is reasonably enhanced from its Standard Model value due to the effect of both Z and Z′ mediated FCNCs, and gives the possibility of new physics beyond the Standard Model. The contribution of Z′ boson depends upon the precise value of MZ′.

scholarly journals On the modelling of energetic multi-jet QCD events

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Daniel Turgeman ◽  
Michael Pitt ◽  
Itamar Roth ◽  
Ehud Duchovni
Keyword(s):  
Standard Model ◽  
State Of The Art ◽  
Data Driven ◽  
Beyond The Standard Model ◽  
Spatial Distributions ◽  
Final State ◽  
Robust Approach ◽  
The Standard Model

AbstractPhysics beyond the Standard Model (BSM) may be unveiled by studying events with a high number of outgoing jets, produced at the LHC with energies above the TeV scale (energetic multi-jet events). Such events are dominated by QCD processes, where the calculations rely on some sort of approximation. Therefore, it is important to develop a robust approach for modeling such events that could probe the existence of BSM signals. In this note, jet spatial distributions in energetic multi-jet processes were compared using several state-of-the-art MC event generators. Slight differences were found, indicating modelling limitations. Therefore, a data-driven technique for the estimation of processes with a final state that contains a large number of jets is proposed. This procedure can predict jet multiplicities up to a precision of  25% in energetic multi-jet events.

scholarly journals Rare CP-violated η and η′ meson decays and neutron EDM.

2018 ◽  
Vol 191 ◽  
pp. 02003
Author(s):  
Alexey S. Zhevlakov ◽  
Mikhail Gorchtein ◽  
Astrid N. Hiller Blin ◽  
Valery E. Lyubovitskij
Keyword(s):  
Dipole Moment ◽  
Standard Model ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Beyond The Standard Model ◽  
Meson Decays ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model

The data for the upper limit on the electric dipole moment of the neutron (nEDM) can be explained by using different mechanisms beyond the Standard Model (SM). The nEDM can be generated by a CP-violating transition of η and η′ mesons into pion pairs. We derive the upper limits for the rates of the CP-violating decays η(η′) → 2π are by orders of magnitude more stringent than those from existing experiments so far.

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