scholarly journals Rare B-meson decays at the crossroads

2016 ◽  
Vol 31 (23) ◽  
pp. 1630036 ◽  
Author(s):  
Ahmed Ali
Keyword(s):  
B Meson ◽  
Branching Fraction ◽  
Theoretical Description ◽  
B Meson Decays ◽  
New Horizons ◽  
The Standard Model ◽  
Standard Candle ◽  
Belle Ii ◽  
Inclusive Decay ◽  
Near Future

Experimental era of rare [Formula: see text]-decays started with the measurement of [Formula: see text] by CLEO in 1993, followed by the measurement of the inclusive decay [Formula: see text] in 1995, which serves as the standard candle in this field. The frontier has moved in the meanwhile to the experiments at the LHC, in particular, LHCb, with the decay [Formula: see text] at about 1 part in 10[Formula: see text] being the smallest branching fraction measured so far. Experimental precision achieved in this area has put the standard model to unprecedented stringent tests and more are in the offing in the near future. I review some key measurements in radiative, semileptonic and leptonic rare [Formula: see text]-decays, contrast them with their estimates in the SM, and focus on several mismatches reported recently. They are too numerous to be ignored, yet, standing alone, none of them is significant enough to warrant the breakdown of the SM. Rare [Formula: see text]-decays find themselves at the crossroads, possibly pointing to new horizons, but quite likely requiring an improved theoretical description in the context of the SM. An independent precision experiment such as Belle II may help greatly in clearing some of the current experimental issues.

Branching Ratio and CP Asymmetry in b→sγ and the Study of Exclusive Radiative B Meson Decays at CLEO

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 632-635
Author(s):  
◽  
Jana B. Thayer
Keyword(s):  
B Meson ◽  
Branching Fraction ◽  
Branching Ratio ◽  
Cp Asymmetry ◽  
B Meson Decays ◽  
Significant Evidence ◽  
Meson Decays ◽  
A Value ◽  
Penguin Decays

We have investigated radiative B meson decays with the CLEO detector. An updated result on the branching fraction ℬ(b→sγ)=(3.15±0.35±0.32 ±0.26)×10-4 is reported. We report on a search for CP asymmetry in b→sγ decays, determining that -0.27<ACP<+0.010 at 90% CL. The measurement of the branching fraction for the exclusive mode B→K*(892)γ has been updated with a value of [Formula: see text] and [Formula: see text] and a first measurement of [Formula: see text] is reported with a value of [Formula: see text]. A search for CP asymmetry in B→K*(892)γ decays yields a measurement of ACP=+0.08±0.13±0.03. We find no significant evidence for the decays B→(ρ/ω)γ and we limit ℬ(B →(ρ/ω)γ)/ℬ(B→K*(892)γ)<0.32 at 90% CL. In addition we find no evidence for the non-penguin decays B0→ϕγ and B0→D*0γ.

scholarly journals η′K PUZZLE OF B MESON DECAYS AND NEW PHYSICS EFFECTS IN THE TC2 MODEL

2001 ◽  
Vol 16 (07) ◽  
pp. 441-455 ◽  
Author(s):  
ZHENJUN XIAO ◽  
WENJUN LI ◽  
GONGRU LU ◽  
LIBO GUO
Keyword(s):  
Standard Model ◽  
B Meson ◽  
New Physics ◽  
Decay Rates ◽  
Low Energy ◽  
Effective Hamiltonian ◽  
B Meson Decays ◽  
The Standard Model ◽  
Model Predictions ◽  
Input Parameters

Using the low energy effective Hamiltonian with the generalized factorization, we calculate the new physics contributions to B→π+π-, Kπ and Kη′ in the topcolor-assisted-technicolor (TC2) model, and compare the results with the available data. By using [Formula: see text] preferred by the CLEO data of B→π+π-decay, we find that the new physics enhancements to B→ Kη′ decays are significant in size, ~ 50% with respect to the standard model predictions, insensitive to the variations of input parameters and hence provide a simple and plausible new physics interpretation for the observed unexpectedly large B→ Kη′ decay rates.

Rare B meson decays to charmed final states at Belle $(B\to D^{(*)} K^-, B^0\to D^+_s \pi^-)$

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 464-467
Author(s):  
◽  
Yangheng Zheng
Keyword(s):  
B Meson ◽  
Branching Fraction ◽  
Final States ◽  
B Meson Decays ◽  
Meson Decays ◽  
Belle Detector ◽  
Upper Limit ◽  
Cabibbo Suppressed

We report observations of the Cabibbo-suppressed decays B→ D(*)K and an upper limit for the decay branching fraction for [Formula: see text] using a 5.3fb-1 data sample accumulated at the ϒ(4S) resonance with the Belle detector at the KEKB e+e- asymmetric collider.

B → K* ℓ+ ℓ- DECAYS WITH POLARIZED K*

2003 ◽  
Vol 18 (08) ◽  
pp. 1443-1448
Author(s):  
C. H. CHEN ◽  
C. Q. GENG
Keyword(s):  
Standard Model ◽  
Heavy Quark ◽  
B Meson ◽  
Form Factors ◽  
Decay Chain ◽  
New Physics ◽  
Effective Theory ◽  
Heavy Quark Effective Theory ◽  
B Meson Decays ◽  
The Standard Model

We study the exclusive decays of B → K* ℓ+ ℓ- within the framework of the PQCD. We obtain the form factors for the B → K* transition in the large recoil region, where the PQCD for heavy B meson decays is reliable. We find that the form factors at q2 = 0 are consistent with those from the large energy effective theory combined with the heavy quark effective theory and the experiment of B → K*γ. Via the decay chain of B → K* (Kπ) ℓ+ ℓ-, we can study many physical observables which are related to the different helicity combinations of B → K* ℓ+ ℓ-, such as the forward-backward asymmetries (FBAs). In particular, we can study the T violating effect which is small in the standard model but can be up to 10% in models with new physics.

A SEARCH FOR B→τν

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 636-638 ◽  
Author(s):  
◽  
JOHN GREGG THAYER
Keyword(s):  
Confidence Level ◽  
B Meson ◽  
Branching Fraction ◽  
Slight Modification ◽  
B Meson Decays ◽  
Meson Decays ◽  
Decay Modes ◽  
Upper Limit ◽  
Charged B Meson

We report results of a search for B→τν in a sample of 9.7 million charged B meson decays. The search uses both πν and [Formula: see text] decay modes of the τ, and demands exclusive reconstruction of the companion [Formula: see text] decay to suppress background. We set an upper limit on the branching fraction ℬ(B→τν)<8.4×10-4 at 90% confidence level. With slight modification to the analysis we also establish [Formula: see text] at 90% confidence level.

scholarly journals Angular and polarization observables for Majorana-mediated B decays with effective interactions

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Lucía Duarte ◽  
Gabriel Zapata ◽  
Oscar A. Sampayo
Keyword(s):  
B Meson ◽  
Effective Field ◽  
B Decays ◽  
B Meson Decays ◽  
Effective Interactions ◽  
Meson Decays ◽  
Vector Interaction ◽  
Lepton Colliders ◽  
The Standard Model ◽  
Polarization Observables

AbstractWe probe the effective field theory extending the Standard Model with a sterile neutrino in B meson decays at B factories and lepton colliders, using angular and polarization observables. We put bounds on different effective operators characterized by their distinct Dirac–Lorentz structure, and probe the N-mediated B decays sensitivity to these interactions. We define a forward–backward asymmetry $$A_\mathrm{FB}^{\ell \gamma }$$ A FB ℓ γ between the muon and photon directions for the $$B \rightarrow \mu \nu \gamma $$ B → μ ν γ decay, which allows us to separate the SM contribution from the effective lepton number conserving and violating processes, mediated by a near on-shell N. Using the most stringent constraints on the effective parameter space from Belle and BaBar we find that a measurement of the final polarization $$P_{\tau }$$ P τ in the rare $$B^-\rightarrow \ell ^-_{1}\ell ^-_{2} \pi ^+$$ B - → ℓ 1 - ℓ 2 - π + decays can help us infer the scalar or vector interaction content in the N production or decay vertices. We find that the B meson decays are more sensitive to scalar operators.

scholarly journals B-meson decays into final states with a τ lepton

2014 ◽  
Vol 29 (07) ◽  
pp. 1430007 ◽  
Author(s):  
Abner Soffer
Keyword(s):  
B Mesons ◽  
B Meson ◽  
Branching Fraction ◽  
Large Data ◽  
New Physics ◽  
Final States ◽  
Initial State ◽  
Lepton Flavor ◽  
Event Reconstruction ◽  
The Standard Model

Decays of B mesons into final states containing a τ lepton are sensitive to new charged current interactions that break lepton-flavor universality. These decays have been studied only at e+e- colliders, where the low-background environment and well-known initial state make it possible to observe small signals with undetectable neutrinos. In particular, the large data samples of the B factories and recent advances in techniques for full-event reconstruction have led to evidence for the decay B+→τ+ ντ and unambiguous observation of the decays [Formula: see text]. These results exclude large regions of the parameter space for a variety of new physics models. Furthermore, the branching fraction for [Formula: see text] has been measured to be higher than the Standard Model expectation by more than three standard deviations, making this an interesting topic for further research. This paper reviews the theoretical and experimental status of this topic, summarizing the results at this time and outlining the path for further improvements.

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