scholarly journals Dark photon from light scalar boson decays at FASER

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
T. Araki ◽  
K. Asai ◽  
H. Otono ◽  
T. Shimomura ◽  
Y. Takubo
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Parameter Space ◽  
Beyond The Standard Model ◽  
Scalar Boson ◽  
Dark Photon ◽  
The Standard Model ◽  
Light Scalar ◽  
Sizable Number

Abstract FASER is one of the promising experiments which search for long-lived particles beyond the Standard Model. In this paper, we focus on dark photon associating with an additional U(1) gauge symmetry, and also a scalar boson breaking this U(1) gauge symmetry. We study the sensitivity to the dark photon originated from U(1)-breaking scalar decays. We find that a sizable number of dark photon signatures can be expected in wider parameter space than previous studies.

scholarly journals Constraining extended scalar sectors at the LHC and beyond

2018 ◽  
Vol 33 (10n11) ◽  
pp. 1830007 ◽  
Author(s):  
Agnieszka Ilnicka ◽  
Tania Robens ◽  
Tim Stefaniak
Keyword(s):  
Dark Matter ◽  
Higgs Boson ◽  
Standard Model ◽  
Parameter Space ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Doublet Model ◽  
Inert Doublet Model ◽  
Scalar Sector ◽  
Scalar Singlet

We give a brief overview of beyond the Standard Model (BSM) theories with an extended scalar sector and their phenomenological status in the light of recent experimental results. We discuss the relevant theoretical and experimental constraints, and show their impact on the allowed parameter space of two specific models: the real scalar singlet extension of the Standard Model (SM) and the Inert Doublet Model. We emphasize the importance of the LHC measurements, both the direct searches for additional scalar bosons, as well as the precise measurements of properties of the Higgs boson of mass 125 GeV. We show the complementarity of these measurements to electroweak and dark matter observables.

Implementation of the CMS-EXO-19-002 search in the MadAnalysis 5 framework (physics beyond the Standard Model with multilepton final states; 137 fb−1)

2021 ◽  
Vol 36 (01) ◽  
pp. 2141012
Author(s):  
Eric Conte ◽  
Robin Ducrocq
Keyword(s):  
Standard Model ◽  
Beyond The Standard Model ◽  
Final States ◽  
Text Data ◽  
Proton Proton ◽  
Original Analysis ◽  
The Standard Model ◽  
Light Scalar ◽  
Charged Leptons ◽  
Proton Proton Collisions

In this paper, we present the MadAnalysis 5 implementation of the CMS-EXO-19-002 analysis, probing an excess of events featuring multiple charged leptons in LHC proton–proton collisions at [Formula: see text]. The original analysis is based on data acquired by the CMS detector during the 2016–2018 campaign, which corresponds to an integrated luminosity of 137 fb[Formula: see text]. Data have been tested against hypothetical extensions of the Standard Model where additional leptons can stem from new heavy fermion decays or from new light scalar/pseudoscalar decays. The CMS selection has been fully implemented in the MadAnalysis 5 platform and successfully validated by reproducing official results in the form of signal distributions at the end of the selection.

scholarly journals An allowed window for heavy neutral leptons below the kaon mass

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Kyrylo Bondarenko ◽  
Alexey Boyarsky ◽  
Juraj Klaric ◽  
Oleksii Mikulenko ◽  
Oleg Ruchayskiy ◽  
...  
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Big Bang ◽  
Majorana Fermions ◽  
Neutrino Masses ◽  
Beyond The Standard Model ◽  
Big Bang Nucleosynthesis ◽  
Kaon Mass ◽  
The Standard Model ◽  
The Universe

Abstract The extension of the Standard Model with two gauge-singlet Majorana fermions can simultaneously explain two beyond-the-Standard-model phenomena: neutrino masses and oscillations, as well as the origin of the matter-antimatter asymmetry in the Universe. The parameters of such a model are constrained by the neutrino oscillation data, direct accelerator searches, big bang nucleosynthesis, and requirement of successful baryogenesis. We show that their combination still leaves an allowed region in the parameter space below the kaon mass. This region can be probed by the further searches of NA62, DUNE, or SHiP experiments.

scholarly journals Lepton Flavor Violation at muon-electron colliders

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Fabio Bossi ◽  
Paolo Ciafaloni
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Z Boson ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Lepton Flavor Violation ◽  
Foreseeable Future ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
The Standard Model

Abstract Lepton Flavor Violating (LFV) processes are clear signals of physics beyond the Standard Model. We investigate the possibility of measuring this kind of processes at present and foreseeable future muon-electron colliders, taking into account present day bounds from existing experiments. As a model of new physics we consider a Z’ boson with a Ut(1) gauge symmetry and generic couplings. Processes that violate lepton flavor by two units seem to be particularly promising.

scholarly journals Scalar leptoquark effects on $$B \rightarrow \mu \bar{\nu }$$ decay

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Wei-Shu Hou ◽  
Tanmoy Modak ◽  
Gwo-Guang Wong
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Low Energy ◽  
Beyond The Standard Model ◽  
Meson Decays ◽  
Scalar Leptoquark ◽  
The Standard Model ◽  
The Impact ◽  
Energy Physics

AbstractPurely leptonic B meson decays provide unique probes for physics Beyond the Standard Model. We study the impact of a scalar leptoquark, $$S_1$$S1, on $$B \rightarrow \mu \bar{\nu }$$B→μν¯ decay. We find that, for $$m_{S_1}\sim 1\ \hbox {TeV}$$mS1∼1TeV, the $$S_1$$S1 leptoquark can modify the $$B \rightarrow \mu \bar{\nu }$$B→μν¯ rate significantly. Such a leptoquark can in principle also alter the $$B \rightarrow \tau \bar{\nu }$$B→τν¯ rate. However, current searches from LHC and low energy physics provide some constraints on the parameter space.

scholarly journals Constraints on the NMSSM from the Oblique Parameters

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Markos Maniatis ◽  
York Schröder
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Gauge Boson ◽  
Precision Measurements ◽  
Supersymmetric Model ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Electroweak Precision ◽  
Minimal Supersymmetric Model

Electroweak precision measurements, encoded in the oblique parameters, give strong constraints on physics beyond the Standard Model. The oblique parametersS,T,U(V,W,X)are calculated in the next-to-minimal supersymmetric model (NMSSM). We outline the calculation of the oblique parameters in terms of one-loop gauge-boson self-energies and find sensitive restrictions for the NMSSM parameter space.

scholarly journals Naturalising the third family hypercharge model for neutral current $$B{-}\hbox {anomalies}$$

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
B. C. Allanach ◽  
Joe Davighi
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Neutral Current ◽  
Beyond The Standard Model ◽  
Yukawa Couplings ◽  
The Third ◽  
Standard Model Contribution ◽  
The Standard Model ◽  
Model Predictions ◽  
Flavour Violation

Abstract We consider a deformation of the Third Family Hypercharge Model, which arguably makes the model more natural. Additional non-zero charges of the spontaneously broken, family-dependent $$U(1)_F$$U(1)F gauge symmetry are assigned to the second family leptons, and the third family leptons’ charges are deformed away from their hypercharges in such a way that the $$U(1)_F$$U(1)F gauge symmetry remains anomaly-free. Second family $$U(1)_F$$U(1)F lepton charges allow a $$Z^\prime $$Z′ coupling to muons without having to assume large charged lepton mixing, which risks violating tight lepton flavour violation bounds. In this deformed version, only the bottom and top Yukawa couplings are generated at the renormalisable level, whereas the tauon Yukawa coupling is absent. The $$Z^\prime $$Z′ mediates a beyond the Standard Model contribution to an effective $$({\bar{b}} s) (\bar{\mu }\mu )$$(b¯s)(μ¯μ) vertex in the combination $$C_9=-9C_{10}$$C9=-9C10 and is able to fit the apparent discrepancy between Standard Model predictions in flavour changing neutral-current $$B-$$B-meson decays and their measurements, whilst simultaneously avoiding current constraints from direct $$Z^\prime $$Z′ searches and other measurements, when $$0.8~\text {TeV}< M_{Z^\prime } < 12.5 ~\text {TeV}$$0.8TeV<MZ′<12.5TeV.

scholarly journals Search for dark forces at KLOE-2

2019 ◽  
Vol 212 ◽  
pp. 06002
Author(s):  
Elena Perez del Rio
Keyword(s):  
Standard Model ◽  
Model Parameters ◽  
Vector Particle ◽  
Beyond The Standard Model ◽  
Final States ◽  
Dark Sector ◽  
Dark Photon ◽  
The Standard Model ◽  
Discovery Potential ◽  
Breaking Mechanism

During the last years several Dark Sector Models have been proposed in order to address striking and puzzling astrophysical observations which fail standard interpretations. In the minimal case a new vector particle, the so called dark photon or U-boson, is introduced, with small coupling with Standard Model particles. Also, the existence of a dark Higgs boson h’ is postulated, in analogy with the Standard Model, to give mass to the U-boson through the Spontaneous Symmetry Breaking mechanism. The discovery of such a Dark Force Mediator would belong to a new field of Physics Beyond the Standard Model. The KLOE experiment, working on the DAΦNE e+e− collider in Frascati, searched for the existence of the U-boson in a quite complete way, investigating several different processes and final states. Tight limits on the model parameters have been set at 90%CL. Further improvements are expected in terms of sensitivity and discovery potential with the new KLOE-2 detector working on the improved DAΦNE e+e− collider, which has collected more than 5 fb−1.

scholarly journals Electroweak phase transitions with BSM fermions

2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Martin Gabelmann ◽  
M. Margarete Mühlleitner ◽  
Jonas Müller
Keyword(s):  
Standard Model ◽  
Degrees Of Freedom ◽  
Higgs Doublet ◽  
Beyond The Standard Model ◽  
Electroweak Phase Transition ◽  
The Standard Model ◽  
Light Scalar ◽  
Doublet Model ◽  
Split Supersymmetry ◽  
The Impact

Abstract We study the impact of additional beyond-the-Standard Model (BSM) fermions, charged under the Standard Model (SM) SU(2)L ⊗ U(1)Y gauge group, on the electroweak phase transition (EWPT) in a 2-Higgs-Doublet-Model (2HDM) of type II. We find that the strength of the EWPT can be enhanced by about 40% compared to the default 2HDM. Therefore, additional light fermions are a useful tool to weaken the tension between increasing mass constraints on BSM scalars and the requirement of additional light scalar degrees of freedom to accommodate a strong first order EWPT. The findings are of particular interest for a variety of (non-minimal) split supersymmetry scenarios which necessarily introduce additional light fermion degrees of freedom.

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