arXiv subjects
Publications and source records attributed to S. Neshatpour.
We describe SuperIso v4.1, a public code for calculation of flavour observables, in the Standard Model and for New Physics scenarios in a model-independent way as well as for specific beyond the SM models such as two Higgs doublet models (2HDM), minimal supersymmetric Standard Model (MSSM) and next-to-minimal supersymmetric Standard Model (NMSSM).
We analyse the results recently presented on the $B^{+} \to K^{*+} μ^+ μ^-$ angular observables by the LHCb Collaboration which show indications for New Physics beyond the Standard Model. Within a model-independent analysis, we compare the fit results with the corresponding results for the angular observables in $B^{0} \to K^{*0} μ^+ μ^-$.
One of the main indications for New Physics in rare $B$-decays is deduced from the tension between experimental and Standard Model predictions of the angular analysis of the $B^0 \to K^{*0} μ^+μ^-$ decay. There are however possible non-local hadronic effects which in principle can also explain these tensions. In this work, we consider a statistical approach for differentiating the source of the tension in $B^0 \to K^{*0} μ^+μ^-$ observables and we also investigate the prospects of such a comparison with future data from the LHCb experiment.
The new angular analysis of the decay $B \to K^* \ell^+ \ell^-$ recently presented by the LHCb Collaboration still indicates some tensions with the Standard Model predictions. There are several ongoing analyses to solve the problem of separating hadronic and New Physics effects in this decay, but the significance of the observed tensions in the angular observables in $B \to K^* μ^+μ^-$ is still dependent on a theory guesstimate of the hadronic contributions to these decays. Using the new data from LHCb we offer two tests which make a statistical comparison to determine whether the most favoured explanation of the anomalies is New Physics or underestimated hadronic effects. We then analyse the usefulness of these tests in two future scenarios. Finally, we update our global fits to all available $b \to s $ data and discuss the impact of the new LHCb measurements.
We present a brief update of our model-independent analyses of the b->s data presented in the articles published in Phys. Rev. D96 (2017) 095034 and Phys. Rev. D98 (2018) 095027 based on new data on R_K by LHCb, on R_{K^*} by Belle, and on B_{s,d}-> mu^+ mu^- by ATLAS.
The LHCb experiment has made several measurements in $b \to s$ transitions which indicate tensions with the Standard Model predictions. Assuming the source of these tensions to be new physics, we present new global fits to all Wilson coefficients which can effectively receive beyond the Standard Model contributions. While the theoretically clean ratios $R_{K^{(*)}}$ which are sensitive to lepton flavour non-universality may unambiguously establish lepton non-universal new physics in the near future, most of the other tensions with the SM in the $b \to s$ data, in particular in the angular observables of the $B\to K^* μμ$ decay and in the branching ratio of the $B_s \to ϕμμ$ decay, depend on the estimates of non-factorisable power corrections. Therefore, we also analyse the dependence of the new global fit on these corrections.
Assuming the source of the anomalies observed recently in $b \to s$ data to be new physics, there is a priori no reason to believe that - in the effective field theory language - only one type of operator is responsible for the tensions. We thus perform for the first time a global fit where all the Wilson coefficients which can effectively receive new physics contributions are considered, allowing for lepton flavour universality breaking effects as well as contributions from chirality flipped and scalar and pseudoscalar operators, and find the SM pull taking into account all effective parameters. As a result of the full fit to all available $b \to s$ data including all relevant Wilson coefficients, we obtain a total pull of 4.1$σ$ with the SM hypothesis assuming 10% error for the power corrections. Moreover, we make a statistical comparison to find whether the most favoured explanation of the anomalies is new physics or underestimated hadronic effects using the most general parameterisation which is fully consistent with the analyticity structure of the amplitudes. This Wilks' test will be a very useful tool to analyse the forthcoming $B\to K^* μ^+ μ^-$ data. Because the significance of the observed tensions in the angular observables in $B \to K^* μ^+μ^-$ is presently dependent on the theory estimation of the hadronic contributions to these decays, we briefly discuss the various available approaches for taking into account the long-distance hadronic effects and examine how the different estimations of these contributions result in distinct significance of the new physics interpretation of the observed anomalies.
The LHCb measurements of certain ratios of decay modes testing lepton flavour non-universality might open an exciting world of new physics beyond the standard model. The latest LHCb measurements of R_K* offer some new insight beyond the previous measurement of R_K. We work out the present significance for non-universality, and argue that claims of 5 sigma deviations from the SM based on all present b -> s l+l- data including the ratios are misleading and are at present still based on guesstimates of hadronic power corrections in the b -> s l+l- angular observables. We demonstrate that only a small part of the luminosity of 50 fb^-1 foreseen to be accumulated by the LHCb will be needed to offer soon a definite answer to the present question whether we see a very small glimpse of lepton flavour non-universal new physics or not. We also present new predictions for other ratios based on our analysis of the present measurements of the ratios R_K^(*) and analyse if they are able to differentiate between various new physics options within the effective field theory at present or in the near future.
The LHCb measurements on the B ->$ K^*$$μ^+ μ^-$ angular observables have shown slight deviations from their Standard Model predictions. The significance of the deviations in the B -> $K^*$$μ^+ μ^-$ decay depends on the assumptions on the size of the non-factorisable power corrections. At present, there are no theoretical predictions on the size of these power corrections in order to identify whether the reason behind these anomalies is due to unknown hadronic corrections or New Physics effects. We have performed a statistical comparison of fitting the data to each of the possible explanations.
The well-known problem of the unknown power corrections within QCD improved factorisation leaves the interpretation of the so-called LHCb anomalies in the angular observables of B-->K* mu+ mu- as an open problem. In order to contribute to the question whether they represent a first sign for new physics beyond the Standard Model or a consequence of underestimated hadronic power corrections, we present a direct comparison of two global fits to the data based on the two different assumptions. In addition, we summarise the possible options to resolve this puzzle in the future.
We discuss the observed deviations in b -> s l+ l- processes from the Standard Model predictions and present global fits for the New Physics description of these anomalies. We further investigate the stability of the global fits under different theoretical assumptions and suggest strategies and a number of observables to clear up the source of the anomalies.
Depending on the assumptions on the power corrections to the exclusive b -> s l+ l- decays, the latest data of the LHCb collaboration - based on the 3 fb^-1 data set and on two different experimental analysis methods - still shows some tensions with the SM predictions. We present a detailed analysis of the theoretical inputs and various global fits to all the available b -> s l+ l- data. This constitutes the first global analysis of the new data of the LHCb collaboration based on the hypothesis that these tensions can be at least partially explained by new physics contributions. In our model-independent analysis we present one-, two-, four-, and also five-dimensional global fits in the space of Wilson coefficients to all available b -> s l+ l- data. We also compare the two different experimental LHCb analyses of the angular observables in B -> K* mu+ mu-. We explicitly analyse the dependence of our results on the assumptions about power corrections, but also on the errors present in the form factor calculations. Moreover, based on our new global fits we present predictions for ratios of observables which may show a sign of lepton non-universality. Their measurements would crosscheck the LHCb result on the ratio R_K = BR(B+ -> K+ mu+ mu-) / BR(B+ -> K+ e+ e-) in the low-q^2 region which deviates from the SM prediction by 2.6 sigma.
There are some slight tensions with the SM predictions within the latest LHCb measurements. Besides the known anomaly in one angular observable of the rare decay B -> K* mu+ mu-, another small discrepancy recently occurred. The ratio R_K = BR(B+ -> K+ mu+ mu-) / BR(B+ -> K+ e+ e-) in the low-q^2 region has been measured by LHCb showing a 2.6 sigma deviation from the SM prediction. In contrast to the anomaly in the rare decay B -> K* mu+ mu- which is affected by power corrections, the ratio R_K is theoretically rather clean. We analyse all the b -> s ll data with global fits and in particular explore the possibility of breaking of lepton universality. Possible cross-checks with an analysis of the inclusive B -> X_s l+ l- decay are also explored.
We provide a detailed analysis of the impact of the newly measured optimised observables in the B -> K* mu+ mu- decay by the LHCb experiment. The analysis is performed in the MSSM, both in the context of the usual constrained scenarios, and in the context of a more general set-up where the SUSY partner masses are independent. We show that the global agreement of the MSSM solutions with the data is still very good. Nevertheless, especially in the constrained scenarios, the limits from B -> K* mu+ mu- are now very strong, and are at the same level as the well-known b -> s gamma constraints. We describe the implications of the B -> K* mu+ mu- measurements both on the Wilson coefficients and on the SUSY parameters.
We study the implications of the recent LHCb limit and results on Bs -> mu+mu- and B -> K* mu+mu- observables in the constrained SUSY scenarios. After discussing the Standard Model predictions and carefully estimating the theoretical errors, we show the constraining power of these observables in CMSSM and NUHM. The latest limit on BR(Bs -> mu+mu-), being very close to the SM prediction, constrains strongly the large tan(beta) regime and we show that the various angular observables from B -> K* mu+mu- decay can provide complementary information in particular for moderate tan(beta) values.