$K_L^0 \to 2\pi $ AND $K_L^0 \to \pi ^0 e^ + e^ - $ WITHOUT CP-VIOLATION

1990 ◽  
Vol 05 (18) ◽  
pp. 1433-1439 ◽  
Author(s):  
SEITARO NAKAMURA ◽  
NOBUYA NAKAZAWA
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Branching Ratio ◽  
K Meson ◽  
The Standard Model ◽  
K Mesons ◽  
Meson System

Neutral K-meson system is analyzed in the framework of SU(2) (isospin: τ)×SU(2) (hypercharge spin: ζ) symmetry. Four neutral K-mesons exist and among them there is a longlived CP-even state which can decay into the 2π or the π0 e+e− state. The branching ratio of the latter mode is expected to be much larger than in the standard model.

scholarly journals Probing new physics with $B^0_s\to\mu^+\mu^-$: Status and perspectives

2014 ◽  
Vol 29 (21) ◽  
pp. 1444004 ◽  
Author(s):  
Robert Fleischer
Keyword(s):  
Standard Model ◽  
Decay Width ◽  
Rare Decay ◽  
Branching Ratio ◽  
New Physics ◽  
High Luminosity ◽  
Width Difference ◽  
Rate Asymmetry ◽  
The Standard Model ◽  
Meson System

The rare decay [Formula: see text] plays a key role for the testing of the Standard Model. It is pointed out that the sizable decay width difference ΔΓsof the Bs-meson system affects this channel in a subtle way. As a consequence, its calculated Standard Model branching ratio has to be upscaled by about 10%. Moreover, the sizable ΔΓsmakes a new observable through the effective [Formula: see text] lifetime accessible, which probes New Physics in a way complementary to the branching ratio and adds an exciting new topic to the agenda for the high-luminosity upgrade of the LHC. Further probes of New Physics are offered by a CP-violating rate asymmetry. Correlations between these observables and the [Formula: see text] branching ratio are illustrated for specific models of New Physics.

scholarly journals Exploring CP-Violation Through B Decays

2003 ◽  
Vol 18 (21) ◽  
pp. 1413-1433 ◽  
Author(s):  
Robert Fleischer
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
B Meson ◽  
Model Description ◽  
B Decays ◽  
Unitarity Triangle ◽  
The Standard Model ◽  
B Factory ◽  
Meson System

The B-meson system provides many strategies to perform stringent tests of the Standard-Model description of CP-violation. In this brief review, we discuss implications of the currently available B-factory data on the angles α, β and γ of the unitarity triangle, emphasize the importance of Bsstudies at hadronic B experiments, and discuss new, theoretically clean strategies to determine γ.

CP Violation

2019 ◽  
pp. 295-312
Author(s):  
Michael E. Peskin
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
B Meson ◽  
Experimental Tests ◽  
K Meson ◽  
Neutral B Meson ◽  
The Standard Model ◽  
T Violation

This chapter describes particle reactions that violate CP and T symmetry, the decay of the neutral K meson and the neutral B meson. It presents the Kobayashi-Maskawa model that explains how the Standard Model can provide a theory of CP and T violation and describes experimental tests of that model.

scholarly journals THEORY OF CP VIOLATION IN THE B-MESON SYSTEM

2002 ◽  
Vol 17 (22) ◽  
pp. 2936-2950 ◽  
Author(s):  
MATTHIAS NEUBERT
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
B Meson ◽  
New Physics ◽  
B Decays ◽  
The Standard Model ◽  
Recent Developments ◽  
Meson System

Recent developments in the theory of CP violation in the B-meson system are reviewed, with focus on the determination of sin 2β from B → J/ψ K decays, its implications for tests of the Standard Model and searches for New Physics, and the determination of γ and α from charmless hadronic B decays.

scholarly journals SPONTANEOUS CP VIOLATION: ALTERNATIVE TO THE STANDARD MODEL

2002 ◽  
Vol 17 (supp01) ◽  
pp. 47-57
Author(s):  
Paul H. Frampton
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Decay Mode ◽  
B Meson ◽  
Branching Ratio ◽  
Neutral Kaon ◽  
Quark Pairs ◽  
Quark Number ◽  
The Standard Model ◽  
New Particles

We propose a model of soft CP violation that evades the strong CP problem and can describe observed CP violation in the neutral kaon sector, both direct and indirect. Our model requires two "duark" mesons carrying quark number two that have complex (CP-violating) bare masses and are coupled to quark pairs. Aside from the existence of these potentially observable new particles with masses of several hundred GeV, we predict a flat unitarily triangle (i.e., no observable direct CP violation in the B-meson sector) and a possibly anomalous branching ratio for the decay mode [Formula: see text].

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 Electroweak-like baryogenesis with new chiral matter

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Kohei Fujikura ◽  
Keisuke Harigaya ◽  
Yuichiro Nakai ◽  
Ruoquan Wang
Keyword(s):  
Phase Transition ◽  
Gauge Symmetry ◽  
Cp Violation ◽  
Standard Model ◽  
Dipole Moments ◽  
Dark Matter Candidate ◽  
Lepton Asymmetry ◽  
First Order ◽  
The Standard Model ◽  
Concrete Realization

Abstract We propose a framework where a phase transition associated with a gauge symmetry breaking that occurs (not far) above the electroweak scale sets a stage for baryogenesis similar to the electroweak baryogenesis in the Standard Model. A concrete realization utilizes the breaking of SU(2)R× U(1)X→ U(1)Y. New chiral fermions charged under the extended gauge symmetry have nonzero lepton numbers, which makes the B − L symmetry anomalous. The new lepton sector contains a large flavor-dependent CP violation, similar to the Cabibbo-Kobayashi-Maskawa phase, without inducing sizable electric dipole moments of the Standard Model particles. A bubble wall dynamics associated with the first-order phase transition and SU(2)R sphaleron processes generate a lepton asymmetry, which is transferred into a baryon asymmetry via the ordinary electroweak sphaleron process. Unlike the Standard Model electroweak baryogenesis, the new phase transition can be of the strong first order and the new CP violation is not significantly suppressed by Yukawa couplings, so that the observed asymmetry can be produced. The model can be probed by collider searches for new particles and the observation of gravitational waves. One of the new leptons becomes a dark matter candidate. The model can be also embedded into a left-right symmetric theory to solve the strong CP problem.

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