scholarly journals Flavor constraints for a vector-like quark of Nelson-Barr type

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
A. L. Cherchiglia ◽  
G. De Conto ◽  
C. C. Nishi
Keyword(s):  
Parameter Space ◽  
Tree Level ◽  
Yukawa Couplings ◽  
Global Fit

Abstract The Nelson-Barr (NB) mechanism to solve the strong CP problem assumes CP conservation, arranges vanishing $$ \overline{\theta} $$ θ ¯ at tree-level and requires vector-like quarks (VLQs) to transmit the CP breaking to the SM. We analyze the flavor constraints coming from the presence of one such down type VLQ of NB type by performing a global fit on the relevant flavor observables. A comparison is made to the case of one generic VLQ. We find that the allowed parameter space for the VLQ Yukawa couplings and the mixing to the SM are confined to a region much smaller than in the generic case, making the NB case falsifiable in principle.

scholarly journals Electroweak corrections in a pseudo Nambu-Goldstone Dark Matter model revisited

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Seraina Glaus ◽  
Margarete Mühlleitner ◽  
Jonas Müller ◽  
Shruti Patel ◽  
Tizian Römer ◽  
...  
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Parameter Space ◽  
Goldstone Boson ◽  
Indirect Evidence ◽  
Tree Level ◽  
Dark Matter Candidate ◽  
Nucleon Scattering ◽  
The Cross ◽  
Electroweak Corrections

Abstract Having so far only indirect evidence for the existence of Dark Matter a plethora of experiments aims at direct detection of Dark Matter through the scattering of Dark Matter particles off atomic nuclei. For the correct interpretation and identification of the underlying nature of the Dark Matter constituents higher-order corrections to the cross section of Dark Matter-nucleon scattering are important, in particular in models where the tree-level cross section is negligibly small. In this work we revisit the electroweak corrections to the dark matter-nucleon scattering cross section in a model with a pseudo Nambu-Goldstone boson as the Dark Matter candidate. Two calculations that already exist in the literature, apply different approaches resulting in different final results for the cross section in some regions of the parameter space leading us to redo the calculation and analyse the two approaches to clarify the situation. We furthermore update the experimental constraints and examine the regions of the parameter space where the cross section is above the neutrino floor but which can only be probed in the far future.

NEUTRINO MASSES AND TeV SCALE RESONANT LEPTOGENESIS FROM SUPERSYMMETRY BREAKING

2006 ◽  
Vol 21 (21) ◽  
pp. 1629-1646 ◽  
Author(s):  
STEPHEN M. WEST
Keyword(s):  
Supersymmetry Breaking ◽  
Mass Matrix ◽  
Mass Splitting ◽  
Light Neutrino ◽  
Tree Level ◽  
Neutrino Masses ◽  
Yukawa Couplings ◽  
Neutrino Sector ◽  
The One ◽  
The Right

We review a class of supersymmetric models in which the light neutrino masses result from higher-dimensional supersymmetry-breaking terms in the MSSM super- and Kähler-potentials. The mechanism used in these models is closely related to the Giudice–Masiero mechanism for the MSSM μ parameter and leads to TeV-scale right-handed neutrino and sneutrino states. In these models, the dominant contribution to the light neutrino (Majorana) mass matrix is a one-loop term with a sub-dominant tree-level "seesaw" contribution. It is also shown that it is possible to construct a natural model of TeV-scale leptogenesis via the resonant behavior of the one-loop self-energy contribution to the right-handed neutrino (Ni) decay. This model addresses the primary problems of previous phenomenological studies of low-energy leptogenesis: a rational for TeV-scale right-handed neutrinos with small Yukawa couplings; the origin of the tiny, but non-zero mass splitting required between at least two Ni masses; and the necessary non-trivial breaking of flavor symmetries in the right-handed neutrino sector.

scholarly journals QUARK MIXING AND CP VIOLATION — THE CKM MATRIX

2006 ◽  
Vol 21 (08n09) ◽  
pp. 1724-1737 ◽  
Author(s):  
ULRICH NIERSTE
Keyword(s):  
Neutral Current ◽  
New Physics ◽  
Tree Level ◽  
B Decays ◽  
Ckm Matrix ◽  
Penguin Decays ◽  
The Status ◽  
First Results ◽  
Global Fit

I summarize the theoretical progress in the determination of the CKM elements since Lepton-Photon 2003 and present the status of the elements and parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix. One finds |Vus| = 0.2227 ± 0.0017 from K and τ decays and |Vcb| = (41.6 ± 0.5) · 10-3 from inclusive semileptonic B decays. The unitarity triangle can now be determined from tree-level quantities alone and the result agrees well with the global fit including flavour-changing neutral current (FCNC) processes, which are sensitive to new physics. From the global fit one finds the three CKM angles θ12 = 12.9° ± 0.1°, θ23 = 2.38° ± 0.03° and θ13 = 0.223° ± 0.007° in the standard PDG convention. The CP phase equals [Formula: see text] at 1σ CL and [Formula: see text] at 2σ CL. A major progress are first results from fully unquenched lattice QCD computations for the hadronic quantities entering the UT fit. I further present the calculation of three-loop QCD corrections to the charm contribution in [Formula: see text] decays, which removes the last relevant theoretical uncertainty from the [Formula: see text] system. Finally I discuss mixing-induced CP asymmetries in [Formula: see text] penguin decays, whose naive average is below its Standard Model value by 3σ.

scholarly journals The Higgs properties in the MSSM after the LHC Run-2

2018 ◽  
Vol 33 (11) ◽  
pp. 1841001
Author(s):  
Jun Zhao
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Supersymmetric Standard Model ◽  
Minimal Supersymmetric Standard Model ◽  
Parameter Space ◽  
Yukawa Couplings ◽  
Gauge Couplings ◽  
Precision Electroweak Data ◽  
Higgs Data

We scrutinize the parameter space of the SM-like Higgs boson in the minimal supersymmetric standard model (MSSM) under current experimental constraints. The constraints are from (i) the precision electroweak data and various flavor observables; (ii) the direct 22 separate ATLAS searches in Run-1; (iii) the latest LHC Run-2 Higgs data and tri-lepton search of electroweakinos. We perform a scan over the parameter space and find that the Run-2 data can further exclude a part of parameter space. For the property of the SM-like Higgs boson, its gauge couplings further approach to the SM values with a deviation below 0.1%, while its Yukawa couplings [Formula: see text] and [Formula: see text] can still sizably differ from the SM predictions by several tens percent.

THE ASSOCIATED PRODUCTION OF THE NEUTRAL TOP-PION WITH A PAIR OF THIRD FAMILY QUARKS AT THE HADRON COLLIDERS

2006 ◽  
Vol 21 (37) ◽  
pp. 2833-2843 ◽  
Author(s):  
XUELEI WANG ◽  
LILI YU ◽  
NAHONG SONG ◽  
WENNA XU
Keyword(s):  
Cross Sections ◽  
The Other ◽  
Tree Level ◽  
Hadron Colliders ◽  
Yukawa Couplings ◽  
The Third ◽  
Flavor Changing ◽  
Associated Production ◽  
Technicolor Model ◽  
The Cross

We study the associated production of the neutral top-pion [Formula: see text] with the third family quarks within the context of the topcolor-assisted technicolor model at the hadron colliders. The studies show that, at the Tevatron, the cross-sections of all these processes are too small to produce enough identified signals. But the cross-sections can be largely enhanced at the LHC. Specially for the processes [Formula: see text] and [Formula: see text], the cross-sections can reach the level of a few hundred fb even a few pb for the light neutral top-pion. With the high yearly luminosity 100 fb-1 at the LHC, over 104 signals can be produced via the above two processes. There exists an ideal flavor-changing mode to detect neutral top-pion, i.e. [Formula: see text], because the SM background of such production mode are very clean. Therefore, we can conclude that neutral top-pion should be observable at the LHC via the processes [Formula: see text] and [Formula: see text]. On the other hand, the statistics available at the LHC via these two processes might be enough to measure the Yukawa couplings [Formula: see text] and [Formula: see text]. Finally, it must be noted that the study of the process [Formula: see text] can give us a good chance to distinguish the TC2 model from the SM and MSSM because there does not exist such similar tree-level favor-changing process in these models.

RADIATIVE CORRECTIONS TO HIGGS MASSES IN THE SUPERSYMMETRIC MODEL WITH AN EXTRA FAMILY AND ANTI-FAMILY

1992 ◽  
Vol 07 (03) ◽  
pp. 187-199 ◽  
Author(s):  
TAKEO MOROI ◽  
YASUHIRO OKADA
Keyword(s):  
Mass Spectrum ◽  
Upper Bound ◽  
Higgs Mass ◽  
Blow Up ◽  
Tree Level ◽  
Supersymmetric Model ◽  
Radiative Corrections ◽  
Yukawa Couplings ◽  
Charged Higgs ◽  
Gut Scale

Radiative corrections to Higgs masses are calculated in a supersymmetric standard model with an extra family and its mirror partners. These corrections, in general, depend on the mass spectrum of fermions, bosons and the strength of Yukawa couplings of the extra families. If we assume that the Yukawa couplings do not blow up below the GUT scale, the upper bound of the lightest Higgs mass increases about 12 GeV. We also notice that, in some cases, the charged Higgs mass becomes lighter than that of the tree level prediction.

The constraints on new physics from b → s transitions

2016 ◽  
Vol 31 (29) ◽  
pp. 1650164
Author(s):  
Zhao-Feng Ge ◽  
Tai-Fu Feng ◽  
Hai-Bin Zhang
Keyword(s):  
Experimental Data ◽  
Parameter Space ◽  
New Physics ◽  
B Decays ◽  
Global Fit ◽  
Rare B Decays

Assuming that the corrections to relevant Wilson coefficients from new physics (NP) contain the possible CP phases, we analyze the constraints on the NP corrections from the updated experimental data on rare B decays from LHCb, BABAR, and BELLE, etc. systematically. Through global fit among the theoretical evaluations and corresponding experimental observations, we find that the possible CP phases of the corrections to relevant Wilson coefficients from NP affect the allowed parameter space obviously.

scholarly journals Exploiting dijet resonance searches for flavor physics

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Marzia Bordone ◽  
Admir Greljo ◽  
David Marzocca
Keyword(s):  
Parameter Space ◽  
Flavor Physics ◽  
New Physics ◽  
Tree Level ◽  
Leading Order ◽  
Meson Decays ◽  
The Way

Abstract In this work, we reinterpret ATLAS and CMS dijet resonance searches to set robust constraints on all hypothetical tree-level scalar and vector mediators with masses up to 5 TeV, assuming a diquark or a quark-antiquark coupling with an arbitrary flavor composition. To illustrate the application of these general results, we quantify the permissible size of new physics in $$ {\overline{B}}_q\to {D}_q^{\left(\ast \right)+}\left\{\pi, K\right\} $$ B ¯ q → D q ∗ + π K consistent with the absence of signal in dijet resonance searches. Along the way, we perform a full SMEFT analysis of the aforementioned non-leptonic B meson decays at leading-order in αs. Our findings uncover a pressing tension between the new physics explanations of recently reported anomalies in these decays and the dijet resonant searches. The high-pT constraints are crucial to drain the parameter space consistent with the low-pT flavor physics data.

scholarly journals Electric dipole moments in the extended scotogenic models

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Motoko Fujiwara ◽  
Junji Hisano ◽  
Chihiro Kanai ◽  
Takashi Toma
Keyword(s):  
Parameter Space ◽  
Electric Dipole ◽  
Dipole Moments ◽  
Mass Hierarchy ◽  
Neutrino Mass Hierarchy ◽  
Electric Dipole Moments ◽  
Yukawa Couplings ◽  
Unitarity Bound ◽  
Charged Leptons ◽  
Electron Edm

Abstract Electric dipole moments (EDMs) of charged leptons arise from a new source of CP violation in the lepton sector. In this paper, we calculate the EDMs of the charged leptons in the minimal scotogenic model with two singlet fermions, and the models extended with one or two triplet fermions instead of the singlet fermions, taking into account the constraints of the neutrino oscillation data, the charged lepton flavor violation and perturbative unitarity bound for the Yukawa couplings. We show that the hybrid model with one singlet and one triplet fermions predicts an electron EDM larger than the other models in both normal and inverted neutrino mass hierarchy. We find some parameter space has already been ruled out by the current upper bound of the electron EDM and further parameter space can be explored by future experiments.

scholarly journals A Sub-GeV Low Mass Hidden Dark Sector of SU(2)H × U(1)X

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Raymundo Ramos ◽  
Van Que Tran ◽  
Tzu-Chiang Yuan
Keyword(s):  
Dark Matter ◽  
Gauge Group ◽  
Parameter Space ◽  
Scalar Potential ◽  
Indirect Detection ◽  
Tree Level ◽  
Dark Matter Candidate ◽  
Dark Photon ◽  
Relic Density ◽  
Low Mass

Abstract We present a detailed study of the non-abelian vector dark matter candidate Wt with a MeV–GeV low mass range, accompanied by a dark photon A′ and a dark Z′ of similar masses, in the context of a gauged two-Higgs-doublet model with the hidden gauge group that has the same structure as the Standard Model electroweak gauge group. The stability of dark matter is protected by an accidental discrete Z2 symmetry (h-parity) which was usually imposed ad hoc by hand. We examine the model by taking into account various experimental constraints including dark photon searches at NA48, NA64, E141, ν-CAL, BaBar and LHCb experiments, electroweak precision data from LEP, relic density from Planck satellite, direct (indirect) detection of dark matter from CRESST-III, DarkSide-50, XENON1T (Fermi-LAT), and collider physics from the LHC. The theoretical requirements of bounded from below of the scalar potential and tree level perturbative unitarity of the scalar sector are also imposed. The viable parameter space of the model consistent with all the constraints is exhibited. While a dark Z′ can be the dominant contribution in the relic density due to resonant annihilation of dark matter, a dark photon is crucial to dark matter direct detection. We also demonstrate that the parameter space can be further probed by various sub-GeV direct dark matter experimental searches at CDEX, NEWS-G and SuperCDMS in the near future.

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