scholarly journals RareBs→γνν-Decay in Family NonuniversalZ′Model

2015 ◽  
Vol 2015 ◽  
pp. 1-5
Author(s):  
Berin Belma Şirvanlı
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Model Parameters ◽  
Photon Polarization ◽  
Polarization Asymmetry ◽  
The Standard Model

The rareBs→γνν-decay with polarized photon is studied in the framework of a family nonuniversalZ′model. The branching ratio and photon polarization asymmetry to the model parameters are calculated and compared with the Standard Model. Deviations from the Standard Model will indicate the presence of new physics.

scholarly journals Searching for new physics in charm radiative decays

2018 ◽  
Vol 33 (32) ◽  
pp. 1850194
Author(s):  
Aritra Biswas ◽  
Sanjoy Mandal ◽  
Nita Sinha
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Radiative Decays ◽  
Symmetric Model ◽  
Leading Order ◽  
Photon Polarization ◽  
Long Distance ◽  
The Standard Model ◽  
Distance Effects

We show that for a heavy vector-like quark model with a down type isosinglet, branching ratio for [Formula: see text] decay is enhanced by more than [Formula: see text] as compared to that in the Standard model when QCD corrections to next-to-leading order are incorporated. In a left–right symmetric model (LRSM) along with a heavy vector-like fermion, enhancement of this order can be achieved at the bare (QCD uncorrected) level itself. We propose that a measurement of the photon polarization could be used to signal the presence of such new physics in spite of the large long distance effects. We find that there is a large region within the allowed parameter space of the model with a vector-like quark and an additional left–right symmetry, where, the photon polarization can be dominantly right-handed.

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.

Study of the semileptonic Bc → ηcτ−v̄τ decay in W′ model

2021 ◽  
Author(s):  
S. Mahata ◽  
P. Maji ◽  
S. Biswas ◽  
S. Sahoo
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Experimental Results ◽  
Lepton Flavor ◽  
The Standard Model ◽  
Text Model

Recently, many discrepancies between the Standard Model (SM) predictions and experimental results have been found in [Formula: see text] quark transitions. Motivated by these discrepancies, we investigated the semileptonic [Formula: see text] decay in [Formula: see text] model. In this paper, we have estimated different decay observables such as branching ratio, lepton flavor universality (LFU) ratio [Formula: see text] and forward–backward asymmetry in the SM as well as in the [Formula: see text] model. In [Formula: see text] model, we find significant deviations from the SM for the observables except for the forward–backward asymmetry. This deviation gives us a possible indication of new physics (NP).

scholarly journals Status of the NA62 Experiment

2020 ◽  
Vol 234 ◽  
pp. 01012
Author(s):  
M. Piccini
Keyword(s):  
Data Analysis ◽  
Standard Model ◽  
Indirect Effects ◽  
Branching Ratio ◽  
New Physics ◽  
Single Event ◽  
Model Framework ◽  
The Standard Model ◽  
Better Than

The decay $ {K^ + } \to {\pi ^ + }v\bar v $, with a very precisely predicted branching ratio of less than 10−10 in the Standard Model framework, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of such decay with a decay-in-flight technique, novel for this channel. The main goal of NA62 is to measure such Branching Ratio of $ {K^ + } \to {\pi ^ + }v\bar v $ with an accuracy better than 20%. This will be achieved by collecting up to 100 $ {K^ + } \to {\pi ^ + }v\bar v $ events with a background contamination at the level of 10%. The NA62 detector was commissioned in 2014 and 2015 and the experiment took physics data from 2015 to 2018. NA62 has already published the result of the 2016 data analysis. The 2017 data analysis is in progress, the single event sensitivity reached and the evaluation of the main backgrounds will be shown in this contribution.

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.

Unparticle effects on B → D(∗)τν

2019 ◽  
Vol 34 (19) ◽  
pp. 1950149
Author(s):  
Jong-Phil Lee
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Experimental Results ◽  
The Standard Model ◽  
Best Fit

We examine the possible unparticle effects on [Formula: see text] associated with [Formula: see text] decays by minimum-[Formula: see text] fitting. Recent measurements from Belle and LHCb are included in this analysis. While it is true that the new experimental results of [Formula: see text] get closer to the Standard Model (SM) predictions, there is still room for new physics and unparticles are also one possibility. Our best-fit values are [Formula: see text] and [Formula: see text], which are still far from the SM values by more than [Formula: see text] or almost [Formula: see text] [Formula: see text]. We also find that the unparticle effects are quite safe to render the branching ratio [Formula: see text] less than 10%.

scholarly journals PROBE THE EFFECTS OF SPLIT SUSY IN RARE B DECAYS

2006 ◽  
Vol 21 (14) ◽  
pp. 1137-1150 ◽  
Author(s):  
CHUAN-HUNG CHEN ◽  
CHAO-QIANG GENG
Keyword(s):  
Standard Model ◽  
Parity Violation ◽  
Branching Ratio ◽  
New Physics ◽  
B Decays ◽  
The Standard Model ◽  
Order Of Magnitude ◽  
Physics Model ◽  
Split Supersymmetry ◽  
New Interactions

We study the decays of B→K(*)ℓ+ℓ- in split supersymmetry with R-parity violation. We find that the decay branching ratio of B→Kτ+τ- in the new physics model due to the scalar interactions can be 1.8×10-6 which is about one order of magnitude larger than in the standard model, whereas those of B→Kℓ+ℓ- (ℓ=e and μ) and the K* modes are insensitive to the new physics. On the other hand, the forward–backward asymmetries of B→Kτ+τ- and Kμ+μ-, vanishing in the standard model, can be over 10 and 1%, respectively. In addition, we show that the new interactions will significantly change the forward–backward asymmetry in B→K*τ+τ-.

scholarly journals An investigation of the very rare $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ decay

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
New Physics ◽  
Single Event ◽  
Data Set ◽  
Upper Limit ◽  
The Standard Model

Abstract The NA62 experiment reports an investigation of the $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ K + → π + ν ν ¯ mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the $$ {K}^{+}\to {\pi}^{+}\nu \overline{\nu} $$ K + → π + ν ν ¯ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of ($$ {0.48}_{-0.48}^{+0.72} $$ 0.48 − 0.48 + 0.72 ) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

scholarly journals TENSION BETWEEN SCALAR/PSEUDOSCALAR NEW PHYSICS CONTRIBUTION TO Bs → μ+μ- AND B → Kμ+μ-

2010 ◽  
Vol 25 (13) ◽  
pp. 1099-1106 ◽  
Author(s):  
ASHUTOSH KUMAR ALOK ◽  
AMOL DIGHE ◽  
S. UMA SANKAR
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Standard Model Prediction ◽  
Branching Ratio ◽  
New Physics ◽  
Strong Constraint ◽  
Maximum Value ◽  
The Standard Model ◽  
Experimental Errors ◽  
Current Bound

New physics in the form of scalar/pseudoscalar operators cannot lower the semileptonic branching ratio Br (B → K μ+μ-) below its standard model value. In addition, we show that the upper bound on the leptonic branching ratio Br (Bs → μ+μ-) sets a strong constraint on the maximum value of Br (B → K μ+μ-) in models with multiple Higgs doublets: with the current bound, Br (B → K μ+μ-) cannot exceed the standard model prediction by more than 2.5%. The conclusions hold true even if the new physics couplings are complex. However, these constraints can be used to restrict new physics couplings only if the theoretical and experimental errors in Br (B → K μ+μ-) are reduced to a few per cent. The constraints become relaxed in a general class of models with scalar/pesudoscalar operators.

scholarly journals EFFECT OF BOTH Z AND Z′ MEDIATED FLAVOR-CHANGING NEUTRAL CURRENTS ON THE BARYONIC RARE DECAY Λb→Λℓ+ℓ-

2009 ◽  
Vol 24 (32) ◽  
pp. 6223-6235 ◽  
Author(s):  
S. SAHOO ◽  
C. K. DAS ◽  
L. MAHARANA
Keyword(s):  
Standard Model ◽  
Z Boson ◽  
Rare Decay ◽  
Branching Ratio ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Neutral Currents ◽  
Flavor Changing ◽  
The Standard Model ◽  
Flavor Changing Neutral Currents

We study the effect of both Z and Z′ mediated flavor-changing neutral currents (FCNCs) on the Λb→Λℓ+ℓ-(ℓ = μ, τ) rare decay. We find the branching ratio is reasonably enhanced from its Standard Model value due to the effect of both Z and Z′ mediated FCNCs, and gives the possibility of new physics beyond the Standard Model. The contribution of Z′ boson depends upon the precise value of MZ′.

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