scholarly journals A self-consistent framework of topological amplitude and its SU(N) decomposition

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Di Wang ◽  
Cai-Ping Jia ◽  
Fu-Sheng Yu
Keyword(s):  
Symmetry Breaking ◽  
Branching Fractions ◽  
Energy Levels ◽  
Heavy Meson ◽  
Flavor Symmetry ◽  
Quark Loop ◽  
Charm Decays ◽  
Decay Channels ◽  
The Standard Model ◽  
Penguin Operator

Abstract We propose a systematic theoretical framework for the topological amplitudes of the heavy meson decays and their SU(N) decomposition. In the framework, the topologies are expressed in invariant tensors and classified into tree- and penguin-operator-induced diagrams according to which four-quark operators, tree or penguin, being inserted into their effective weak vertexes. The number of possible topologies contributing to one type of decay can be counted by permutations and combinations. The Wigner-Eckhart theorem ensures the topological amplitudes under flavor symmetry are the same for different decay channels. By decomposing the four-quark operators into irreducible representations of SU(N) group, one can get the SU(N) irreducible amplitudes. Taking the D → PP decay (P denoting a pseudoscalar meson) with SU(3)F symmetry as an example, we present our framework in detail. The linear correlation of topologies in the SU(3)F limit is clarified in group theory. It is found there are only nine independent topologies in all tree- and penguin-operator-induced diagrams contributing to the D → PP decays in the Standard Model. If a large quark-loop diagram, named TLP, is assumed, the large ∆ACP and the very different D0→ K+K− and D0→ π+π− branching fractions can be explained with a normal U-spin breaking. Moreover, our framework provides a simple way to analyze the SU(N) breaking effects. The linear SU(3)F breaking and the high order U-spin breaking in charm decays are re-investigated in our framework, which are consistent with literature. Analogous to the degeneracy and splitting of energy levels, we propose the concepts of degeneracy and splitting of topologies to describe the flavor symmetry breaking effects in decay. As applications, we analyze the strange-less D decays in SU(3)F symmetry breaking into Isospin symmetry and the charm-less B decays in SU(4)F symmetry breaking into SU(3)F symmetry.

Flavons and LFV decays and productions of pseudoscalar mesons

2019 ◽  
Vol 34 (35) ◽  
pp. 1950288
Author(s):  
Tian-Qi Li ◽  
Chong-Xing Yue
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Flavor Symmetry ◽  
Lepton Flavor ◽  
Flavor Changing ◽  
Pseudoscalar Mesons ◽  
The Standard Model

Flavons are the dynamic agent of flavor symmetry breaking and have flavor changing couplings to the Standard Model (SM) fermions. We consider their contributions to the lepton flavor violating (LFV) decays [Formula: see text] and [Formula: see text] with [Formula: see text], [Formula: see text] or [Formula: see text] and [Formula: see text] in the simplest flavon model without Higgs-flavon mixing. We find that flavons can produce significant contributions to some of these LFV decay processes.

scholarly journals $K_{\rm L}\to \pi^0\nu\bar\nu$ AS A PROBE OF NEW PHYSICS

2006 ◽  
Vol 21 (03) ◽  
pp. 487-504 ◽  
Author(s):  
DOUGLAS BRYMAN ◽  
ANDRZEJ J. BURAS ◽  
GINO ISIDORI ◽  
LAURENCE LITTENBERG
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Symmetry Breaking ◽  
New Physics ◽  
Flavor Symmetry ◽  
Beyond The Standard Model ◽  
Theoretical Virtues ◽  
Unique Role ◽  
The Standard Model

We summarize the theoretical virtues of the rare [Formula: see text] decays and emphasize the unique role of [Formula: see text] in probing the nature of physics beyond the Standard Model, in particular concerning possible new sources of CP violation and flavor-symmetry breaking. A brief summary of the prospects for the measurement of the [Formula: see text] rate is also given.

scholarly journals Two-body charmed baryon decays involving decuplet baryon in the quark-diagram scheme

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Y. K. Hsiao ◽  
Qian Yi ◽  
Shu-Ting Cai ◽  
H. J. Zhao
Keyword(s):  
Pseudoscalar Meson ◽  
Branching Fractions ◽  
Flavor Symmetry ◽  
Isospin Symmetry ◽  
Charmed Baryon ◽  
Decay Channels ◽  
Decuplet Baryon ◽  
Exchange Processes ◽  
Quark Diagram ◽  
Cabibbo Suppressed

AbstractIn the quark-diagram scheme, we study the charmed baryon decays of $$\mathbf{B}_c\rightarrow \mathbf{B}^* M$$ B c → B ∗ M , where $$\mathbf{B}_c$$ B c is $$\Lambda _c^+$$ Λ c + or $$\Xi _c^{+(0)}$$ Ξ c + ( 0 ) , together with $$\mathbf{B}^*$$ B ∗ (M) the decuplet baryon (pseudoscalar meson). It is found that only two W-exchange processes are allowed to contribute to $$\mathbf{B}_c\rightarrow \mathbf{B}^* M$$ B c → B ∗ M . Particularly, we predict $${\mathcal {B}}(\Lambda _c^+ \rightarrow \Sigma ^{*0(+)} \pi ^{+(0)})=(2.8\pm 0.4)\times 10^{-3}$$ B ( Λ c + → Σ ∗ 0 ( + ) π + ( 0 ) ) = ( 2.8 ± 0.4 ) × 10 - 3 , which respects the isospin symmetry. Besides, we take into account the SU(3) flavor symmetry breaking, in order to explain the observation of $${\mathcal {B}}(\Lambda _c^+\rightarrow \Sigma ^{*+}\eta )$$ B ( Λ c + → Σ ∗ + η ) . For the decays involving $$\Delta ^{++}(uuu)$$ Δ + + ( u u u ) , we predict $${\mathcal {B}}(\Lambda _c^+\rightarrow \Delta ^{++} \pi ^-,\Xi _c^+ \rightarrow \Delta ^{++} K^-) =(7.0\pm 1.4,13.5\pm 2.7)\times 10^{-4}$$ B ( Λ c + → Δ + + π - , Ξ c + → Δ + + K - ) = ( 7.0 ± 1.4 , 13.5 ± 2.7 ) × 10 - 4 as the largest branching fractions in the singly Cabibbo-suppressed $$\Lambda _c^+,\Xi _c^+\rightarrow \mathbf{B}^*M$$ Λ c + , Ξ c + → B ∗ M decay channels, respectively, which are accessible to the LHCb, BELLEII and BESIII experiments.

scholarly journals Exploring color-octet scalar parameter space in minimal R-symmetric models

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Linda M. Carpenter ◽  
Taylor Murphy ◽  
Matthew J. Smylie
Keyword(s):  
Large Hadron Collider ◽  
Parameter Space ◽  
Branching Fractions ◽  
Hadron Collider ◽  
Collider Phenomenology ◽  
Decay Channels ◽  
Color Octet ◽  
Supersymmetric Models ◽  
Three Body ◽  
Displaced Vertex

Abstract In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous R symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.

scholarly journals Exothermic dark mesons in light of electron recoil excess at XENON1T

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Soo-Min Choi ◽  
Hyun Min Lee ◽  
Bin Zhu
Keyword(s):  
Dark Matter ◽  
Inelastic Scattering ◽  
Small Mass ◽  
Density Current ◽  
Flavor Symmetry ◽  
Color Group ◽  
Dark Sector ◽  
The Standard Model ◽  
Electron Recoil ◽  
Relic Density

Abstract We consider a novel mechanism to realize exothermic dark matter with dark mesons in the limit of approximate flavor symmetry in a dark QCD. We introduce a local dark U(1)′ symmetry to communicate between dark mesons and the Standard Model via Z′ portal by partially gauging the dark flavor symmetry with flavor-dependent charges for cancelling chiral anomalies in the dark sector. After the dark local U(1)′ is broken spontaneously by the VEV of a dark Higgs, there appear small mass splittings between dark quarks, consequently, leading to small split masses for dark mesons, required to explain the electron recoil excess in XENON1T by the inelastic scattering between dark mesons and electron. We propose a concrete benchmark model for split dark mesons based on SU(3)L× SU(3)R/SU(3)V flavor symmetry and SU(Nc) color group and show that there exists a parameter space making a better fit to the XENON1T data with two correlated peaks from exothermic processes and satisfying the correct relic density, current experimental and theoretical constraints.

scholarly journals Search for decays of the 125 GeV Higgs boson into a Z boson and a ρ or ϕ meson

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
A. M. Sirunyan ◽  
◽  
A. Tumasyan ◽  
W. Adam ◽  
F. Ambrogi ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Z Boson ◽  
Branching Fractions ◽  
Proton Collision ◽  
Data Set ◽  
Proton Proton ◽  
Decay Channels ◽  
Decay Products ◽  
Upper Limits ◽  
Z Boson Decays

Abstract Decays of the 125 GeV Higgs boson into a Z boson and a ρ0(770) or ϕ(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at $$ \sqrt{s} $$ s = 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb−1. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the ρ and ϕ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and ρ or ϕ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Zρ and Zϕ are determined to be 1.04–1.31% and 0.31–0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740–940 and 730–950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.

scholarly journals Chiral anomaly in SU(2)R-axion inflation and the new prediction for particle cosmology

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Azadeh Maleknejad
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Particle Physics ◽  
Cosmological Parameters ◽  
Chiral Anomaly ◽  
Dark Matter Candidate ◽  
Neutrino Sector ◽  
Matter Creation ◽  
The Standard Model ◽  
Non Gaussian

Abstract Upon embedding the axion-inflation in the minimal left-right symmetric gauge extension of the SM with gauge group SU(2)L × SU(2)R × U(1)B−L, [1] proposed a new particle physics model for inflation. In this work, we present a more detailed analysis. As a compelling consequence, this setup provides a new mechanism for simultaneous baryogenesis and right-handed neutrino creation by the chiral anomaly of WR in inflation. The lightest right-handed neutrino is the dark matter candidate. This setup has two unknown fundamental scales, i.e., the scale of inflation and left-right symmetry breaking SU(2)R × U(1)B−L→ U(1)Y. Sufficient matter creation demands the left-right symmetry breaking scale happens shortly after the end of inflation. Interestingly, it prefers left-right symmetry breaking scales above 1010 GeV, which is in the range suggested by the non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right symmetry scale. Although WR gauge field generates equal amounts of right-handed baryons and leptons in inflation, i.e. B − L = 0, in the Standard Model sub-sector B − LSM ≠ 0. A key aspect of this setup is that SU(2)R sphalerons are never in equilibrium, and the primordial B − LSM is conserved by the Standard Model interactions. This setup yields a deep connection between CP violation in physics of inflation and matter creation (visible and dark); hence it can naturally explain the observed coincidences among cosmological parameters, i.e., ηB ≃ 0.3Pζ and ΩDM ≃ 5ΩB. The new mechanism does not rely on the largeness of the unconstrained CP-violating phases in the neutrino sector nor fine-tuned masses for the heaviest right-handed neutrinos. The SU(2)R-axion inflation comes with a cosmological smoking gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which can be probed by future CMB missions and laser interferometer detectors.

scholarly journals THE PROBLEM OF NEUTRINO MASSES IN EXTENSIONS OF THE STANDARD MODEL

2001 ◽  
Vol 16 (32) ◽  
pp. 5101-5199 ◽  
Author(s):  
ISABELLA MASINA
Keyword(s):  
Proton Decay ◽  
Fine Tuning ◽  
Neutrino Masses ◽  
Flavor Symmetry ◽  
Mixing Angle ◽  
Grand Unified Theories ◽  
Triplet Splitting ◽  
Fermion Masses ◽  
The Standard Model ◽  
Neutrino Masses And Mixings

We review the problem of neutrino masses and mixings in the context of grand unified theories. After a brief summary of the present experimental status of neutrino physics, we describe how the see-saw mechanism can automatically account for the large atmospheric mixing angle. We provide two specific examples where this possibility is realized by means of a flavor symmetry. We then review in some detail the various severe problems which plague minimal GUT models (like the doublet–triplet splitting and proton-decay) and which force us to investigate the possibility of constructing more elaborate but realistic models. We then show an example of a quasirealistic SUSY SU(5) model which, by exploiting the crucial presence of an Abelian flavor symmetry, does not require any fine-tuning and predicts a satisfactory phenomenology with respect to coupling unification, fermion masses and mixings and bounds from proton decay.

scholarly journals RECENT τ LEPTON RESULTS FROM BABAR

2014 ◽  
Vol 35 ◽  
pp. 1460440
Author(s):  
ALBERTO LUSIANI
Keyword(s):  
Standard Model ◽  
Branching Fractions ◽  
Charged Particles ◽  
Babar Collaboration ◽  
Final States ◽  
Final State ◽  
Experimental Knowledge ◽  
Electron Positron ◽  
The Standard Model ◽  
Positron Collisions

We report recent measurements on τ leptons obtained by the BABAR collaboration using the entire recorded sample of electron-positron collisions at and around the Υ(4S) (about 470fb-1). The events were recorded at the PEP-II asymmetric collider at the SLAC National Accelerator Laboratory. The measurements include high multiplicity τ decay branching fractions with 3 or 5 charged particles in the final state, a search for the second class current the τ decay τ → πη′ν, τ branching fractions into final states containing two KS mesons, [Formula: see text], with h = π, K, and preliminary measurements of hadronic spectra of τ decays with three hadrons (τ- → h-h+h-ντ decays, where h = π, K). The results improve the experimental knowledge of the τ lepton properties and can be used to improve the precision tests of the Standard Model.

scholarly journals Flavor symmetry breaking in the 1/Ncexpansion

1996 ◽  
Vol 53 (1) ◽  
pp. 273-282 ◽  
Author(s):  
Jin Dai ◽  
Roger Dashen ◽  
Elizabeth Jenkins ◽  
Aneesh V. Manohar
Keyword(s):  
Symmetry Breaking ◽  
Flavor Symmetry
Sign in / Sign up

Export Citation Format

Share Document