Comparative analysis of the Λb→Λℓ+ℓ−\Lambda_b \rightarrow \Lambda \ell^+ \ell^- decay in the SM, SUSY and RS model with custodial protection

We comparatively analyze the rare $\Lambda _b\rightarrow \Lambda \ell^+ \ell^-$ channel in standard model, supersymmetry and Randall-Sundrum model with custodial protection (RS$_c$). Using the parametrization of the matrix elements entering the low energy effective Hamiltonian in terms of form factors, we calculate the corresponding differential decay width and lepton forward-backward asymmetry in these models. We compare the results obtained with the most recent data from LHCb as well as lattice QCD results on the considered quantities. It is obtained that the standard model, with the form factors calculated in light-cone QCD sum rules, can not reproduce some experimental data on the physical quantities under consideration but the supersymmetry can do it. The RS$_c$ model predictions are roughly the same as the standard model and there are no considerable differences between the predictions of these two models. In the case of differential decay rate, the data in the range $4$ GeV$^2/$c$^4\leq$ $q^2 \leq 6$ GeV$^2/$c$^4$ can not be described by any of the considered models.Comment: 28 Pages, 12 Figures and 3 Table

Analysis of the semileptonic Λb→Λℓ+ℓ−\Lambda_b\rightarrow \Lambda \ell^+ \ell^- transition in topcolor-assisted technicolor (TC2) model

We comparatively analyze the flavor changing neutral current process of the $\Lambda_b \rightarrow \Lambda \ell^+ \ell^-$ in the standard model as well as topcolor-assisted technicolor model using the form factors calculated via light cone QCD sum rules in full theory. In particular, we calculate the decay width, branching ratio and lepton forward-backward asymmetry related to this decay channel. We compare the results of the topcolor-assisted technicolor model with those of the standard model and debate how the results of the topcolor-assisted technicolor model depart from the standard model predictions. We also compare our results on the differential branching ratio with recent experimental data provided by CDF and LHCb Collaborations.Comment: 29 Pages, 16 Figures and 8 Table

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

PANDA Phase One - PANDA collaboration

The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or P¯ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper

Effects of vector leptoquarks on Lambda(b) -> Lambda(c)l(v)over-bar(l) decay

Experimental data on, R(D-(*()), R(K-(*()), and R(J/psi),, provided by different collaborations, show sizable deviations from the standard model predictions. To describe these anomalies, many new physics scenarios have been proposed. One of them is the leptoquark model, which introduces the simultaneous coupling of vector and scalar leptoquarks to quarks and leptons. To look for similar possible anomalies in the baryonic sector, we investigate the effects of a vector leptoquark U-3(3, 3, 2/3) on various physical quantities related to the tree-level Lambda b -> Lambda(c)l (v) over bar (l) decays (l = mu, tau), which proceed via b -> cl (v) over bar (l) transitions at the quark level. We calculate the differential branching ratio, forward-backward asymmetry, and longitudinal polarizations of leptons and Lambda(c) baryons at the mu and tau lepton channels in the leptoquark model and compare their behavior to the predictions of the SM in terms of q(2). In the calculations, we use the form factors calculated in full QCD as the main input and account for all errors coming from the form factors and model parameters. We observe that at the tau channel, the R-A fit solution to data related to the leptoquark model sweeps some regions out of the SM band; nevertheless, the fit has a considerable intersection with the SM predictions. The R-B type solution gives roughly the same results as the SM on DBR(q(2)) - q(2). At the mu channel, the leptoquark model gives results that are consistent with the SM predictions and existing experimental data on the behavior of DBR(q(2)) with respect to q(2). Concerning the q(2) behavior of the AFB(q(2)), the two types of fits for and the predictions at the mu channel in the leptoquark model give exactly the same results as the SM. We also investigate the behavior of the parameter R(q(2)) with respect to q(2) and the value of R(Lambda(c)) in both the vector leptoquark and SM models. Both fit solutions lead to results that deviate considerably from the SM predictions for R(q(2)) - q(2) and R(Lambda(c)). Future experimental data on R(q(2)) - q(2) and R(Lambda(c)), made available by measurements of the Lambda(b) -> Lambda(c)tau(nu) over bar tau channel, will be particularly helpful. Any experimental deviations from the SM predictions in this channel would emphasize the importance of tree-level hadronic weak transitions as good probes of new physics effects beyond the SM

Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR

This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented

Study of Excited Ξ\Xi Baryons with the PANDA Detector

The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards $N^*$ and $\Delta$ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the $N^*$ and $\Delta$ spectra. The future antiproton experiment PANDA will provide direct access to final states containing a $\bar{\Xi}\Xi$ pair, for which production cross sections up to $\mu$b are expected in $\bar{p}p$ reactions. With a luminosity of $L=10^{31}\,cm^{-2}s^{-1}$ in the first phase of the experiment, the expected cross sections correspond to a production rate of $\sim 10^6$ events$/$day. With a nearly $4\pi$ detector acceptance, PANDA will thus be a hyperon factory. In this study, reactions of the type $\bar{p}p\rightarrow \bar{\Xi}^+ \Xi^{*-}$ as well as $\bar{p}p\rightarrow \bar{\Xi}^{*+} \Xi^{-}$ with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between $3\,\%$ and $5\,\%$. This allows high statistics data to be collected within a few weeks of data taking

Study of excited Ξ baryons with the P¯ ANDA detector

The study of baryon excitation spectra provides insight into the inner structure of baryons. So far, most of the world-wide efforts have been directed towards N∗ and Δ spectroscopy. Nevertheless, the study of the double and triple strange baryon spectrum provides independent information to the N∗ and Δ spectra. The future antiproton experiment P¯ANDA will provide direct access to final states containing a Ξ¯ Ξ pair, for which production cross sections up to μb are expected in p¯p reactions. With a luminosity of L= 10 31 cm- 2 s- 1 in the first phase of the experiment, the expected cross sections correspond to a production rate of ∼106events/day. With a nearly 4 π detector acceptance, P¯ANDA will thus be a hyperon factory. In this study, reactions of the type p¯p → Ξ¯ +Ξ∗ - as well as p¯p → Ξ¯ ∗ +Ξ- with various decay modes are investigated. For the exclusive reconstruction of the signal events a full decay tree fit is used, resulting in reconstruction efficiencies between 3 and 5%. This allows high statistics data to be collected within a few weeks of data taking