Search for π0 decays to invisible particles

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.

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Search for New Particles Decaying into $b \bar{b}$ Associated with W± Bosons at Tevatron

International Journal of Modern Physics A ◽

10.1142/s0217751x05026376 ◽

2005 ◽

Vol 20 (15) ◽

pp. 3294-3296

Author(s):

◽

Yoshio Ishizawa

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Cross Section ◽

Production Cross ◽

W Bosons ◽

Branching Ratio ◽

Standard Model Higgs Boson ◽

Upper Limit ◽

The Standard Model ◽

New Particles

We present searches for new particles decaying into [Formula: see text] and produced in association with W± bosons in [Formula: see text] collisions at [Formula: see text]. The searches focus on the Standard Model Higgs boson or Technicolor particle decaying into [Formula: see text] using approximately 162 pb-1 of the dataset accumulated by the Collider Detector at Fermilab. The number of events and mass distribution are consistent with the Standard Model expectations and we set a 95% confidence level upper limit on the production cross section times branching ratio as a function of the new particle mass.

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Search for dark photons in Higgs boson production via vector boson fusion in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

Journal of High Energy Physics ◽

10.1007/jhep03(2021)011 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

A. M. Sirunyan ◽

◽

A. Tumasyan ◽

W. Adam ◽

T. Bergauer ◽

...

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Confidence Level ◽

Branching Fraction ◽

Vector Boson ◽

Boson Mass ◽

Higgs Boson Mass ◽

Vector Boson Fusion ◽

Upper Limit ◽

The Standard Model

Abstract A search is presented for a Higgs boson that is produced via vector boson fusion and that decays to an undetected particle and an isolated photon. The search is performed by the CMS collaboration at the LHC, using a data set corresponding to an integrated luminosity of 130 fb−1, recorded at a center-of-mass energy of 13 TeV in 2016–2018. No significant excess of events above the expectation from the standard model background is found. The results are interpreted in the context of a theoretical model in which the undetected particle is a massless dark photon. An upper limit is set on the product of the cross section for production via vector boson fusion and the branching fraction for such a Higgs boson decay, as a function of the Higgs boson mass. For a Higgs boson mass of 125 GeV, assuming the standard model production rates, the observed (expected) 95% confidence level upper limit on the branching fraction is 3.5 (2.8)%. This is the first search for such decays in the vector boson fusion channel. Combination with a previous search for Higgs bosons produced in association with a Z boson results in an observed (expected) upper limit on the branching fraction of 2.9 (2.1)% at 95% confidence level.

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Search for Heavy Higgs Bosons in Fermionic Decay Channels with CMS

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194518600583 ◽

2018 ◽

Vol 46 ◽

pp. 1860058

Author(s):

Ye Chen

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Confidence Level ◽

Higgs Bosons ◽

Final States ◽

Centre Of Mass ◽

Decay Channels ◽

Upper Limits ◽

The Standard Model ◽

Cms Detector

Latest results of searches for heavy Higgs bosons in fermionic final states are presented using the CMS detector at the LHC. Results are based on pp collision data collected at centre-of-mass energies of 8 and 13 TeV which have been interpreted according to different extensions of the Standard Model such as MSSM, 2HDM, and NMSSM. These searches look for evidence of other scalar or pseudoscalar bosons, in addition to the observed SM-like 125 GeV Higgs boson, and set 95% confidence level upper limits in fermionic final states and benchmark models explored. The talk reviews briefly the major results obtained by the CMS Collaboration during Run I, and presents the most recent searches performed during Run II.

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THE STRENGTH OF TRILINEAR HIGGS BOSON COUPLING IN COMPOSITE MODELS

International Journal of Modern Physics E ◽

10.1142/s0218301307008860 ◽

2007 ◽

Vol 16 (09) ◽

pp. 2979-2983 ◽

Cited By ~ 1

Author(s):

A. DOFF ◽

A. A. NATALE

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Standard Model Higgs Boson ◽

Self Energy ◽

The Standard Model ◽

Composite Models ◽

Model Independent ◽

Boson Coupling ◽

The One

In this work we discuss the strength of the trilinear Higgs boson coupling in composite models in a model independent way. The coupling is determined as a function of a very general ansatz for the fermionic self-energy, and turns out to be equal or smaller than the one of the Standard Model Higgs boson depending on the dynamics of the theory.

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A search for the dimuon decay of the Standard Model Higgs boson with the ATLAS detector

Physics Letters B ◽

10.1016/j.physletb.2020.135980 ◽

2021 ◽

Vol 812 ◽

pp. 135980

Author(s):

G. Aad ◽

B. Abbott ◽

D.C. Abbott ◽

A. Abed Abud ◽

K. Abeling ◽

...

Keyword(s):

Higgs Boson ◽

Standard Model ◽

Atlas Detector ◽

Standard Model Higgs Boson ◽

The Standard Model

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Search for dark matter in association with an energetic photon in pp collisions at $$ \sqrt{s} $$ = 13 TeV with the ATLAS detector

Journal of High Energy Physics ◽

10.1007/jhep02(2021)226 ◽

2021 ◽

Vol 2021 (2) ◽

Author(s):

G. Aad ◽

◽

B. Abbott ◽

D. C. Abbott ◽

A. Abed Abud ◽

...

Keyword(s):

Dark Matter ◽

Transverse Momentum ◽

Standard Model ◽

Confidence Level ◽

Axial Vector ◽

Beyond The Standard Model ◽

Proton Proton ◽

Missing Transverse Momentum ◽

Upper Limits ◽

The Standard Model

Abstract A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb−1. No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling gaZγ of an axion-like particle to the electroweak gauge bosons.

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

Journal of High Energy Physics ◽

10.1007/jhep04(2021)158 ◽

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.

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