In this paper we show that the excess of the tau tau events with respect to the Standard Model background predictions, observed by the ATLAS and CMS collaborations and interpreted as the evidence of the Higgs-boson decay into a pair of tau-leptons, may be accounted for by properly taking into account QED radiative corrections in the modelling of the Z/gamma* -> tau tau background.
We present an analytic calculation of electron and tau O(alpha^3) loop effects on the muon anomalous magnetic moment. Computation of such three-loop diagrams with three mass scales is possible using asymptotic and eikonal expansions. An evaluation of a new type of eikonal integrals is presented in some detail.
Searches for lepton flavor violation in tau decays are unambiguous signatures of new physics. The branching ratios of tau leptons at the level of 10^-10 - 10^-9 can be probed with 50 ab^-1 of electron-positron annihilation data being collected by the Belle II experiment at the world's highest luminosity accelerator, the SuperKEKB, located at the High Energy Accelerator Research Organization, KEK, in Tsukuba, Japan. Searches with such expected sensitivity will either discover new physics or strongly constrain several new physics models.
The mass of the Standard Model (SM) Higgs boson was constrained by the Large Electron-Positron (LEP) collider to be above 114.4 GeV. Simple extensions of the scalar sector like adding singlets and/or doublets allow the lightest Higgs to be much lighter via a reduction in its coupling to gauge bosons. Such a light Higgs could have evaded the LEP searches but could be detected at the Large Hadron Collider (LHC) in the process pp -> h j -> tau^+ tau^- j, where j is a resolved jet. We conclude that in some Beyond the Standard Model (BSM) extensions of the scalar sector, a very light Higgs state co…
The "true muonium" (mu^+ mu-) and "true tauonium" (tau^+ tau^-) bound states are not only the heaviest, but also the most compact pure QED systems. The rapid weak decay of the tau makes the observation of true tauonium difficult. However, as we show, the production and study of true muonium is possible at modern electron-positron colliders.
The tau lepton can be more composite than naively expected in models of strong electroweak symmetry breaking with tri-bimaximal lepton mixing. New leptonic resonances required by custodial symmetry, the tau custodians, can then be the first signal of this lepton flavor realization. Tau custodians can be very light, decaying almost exclusively into taus. The LHC reach for these new leptons is up to masses of 240, 480 and 720 GeV for sqrt{s}=14 TeV and an integrated luminosity of 30, 300 and 3000 fb^{-1}, respectively. Our analysis can be extended to any pair produced particles decaying mostly i…
We confront the indications of lepton flavor universality (LFU) violation observed in semi-tauonic $B$ meson decays with new physics (NP) searches using high $p_T$ tau leptons at the LHC. Using effective field theory arguments we correlate possible non-standard contributions to semi-tauonic charged currents with the $τ^+ τ^-$ signature at high energy hadron colliders. Several representative standard model extensions put forward to explain the anomaly are examined in detail: (i) weak triplet of color-neutral vector resonances, (ii) second Higgs doublet and (iii) scalar or (iv) vector leptoquark…
Improved values for the two- and three-loop mass-dependent QED contributions to the anomalous magnetic moments of the electron, muon, and tau lepton are presented. The Standard Model prediction for the electron (g-2) is compared with its most precise recent measurement, providing a value of the fine-structure constant in agreement with a recently published determination. For the tau lepton, differences with previously published results are found and discussed. An updated value of the fine-structure constant is presented in "Note added after publication."
We study the possibilities offered by muon storage rings for tau-neutrino appearance experiments due to nu_mu to nu_tau and nu_e to nu_tau oscillations. Tau event rates for such experiments are first discussed with a view to examining their variation prior to the inclusion of experimental cuts, in order to better understand how baselines, beam energies, forward peaking of decay neutrinos with increasing energies and average fluxes intercepted by detectors of various sizes can affect their optimization. Subsequently, event rates implementing cuts are computed for hadronic and wrong-sign lepton …
We show that single photon searches at LEP constrain the tau neutrino magnetic moment to be less than ${\cal O}(10^{-6})~μ_B$. This bound is competitive with low energy ($s\simeq (30~GeV)^2$) single photon searches.
Searches for heavy neutrinos often rely on the possibility that the heavy neutrinos will decay to detectable particles. Interpreting the results of such searches requires a particular model for the heavy-neutrino decay. We present a method for placing limits on the probability that a tau can couple to a heavy neutrino, |U_tau4|^2, using only the kinematics of semi-leptonic tau decays, instead of a specific model. Our study suggests that B factories with large datasets, such a Belle and BaBar, may be able to place stringent limits on |U_tau4|^2 as low as O(10^-7 - 10^-3) when 100 MeV < m_4 < 1.…
We discuss the physics case for direct searches at the LHC motivated by the $B$-physics anomalies. After correlating semi-tauonic $B$ decays to di-tau production at the LHC, and discussing the possible models solving the $B$-anomalies, we show how current LHC data in $τ\barτ$ tails exclude most beyond the SM scenarios except for a handful of leptoquark (LQ) models. We analyze in detail the impact of LHC searches for some of these LQ solutions using current data. In particular, we focus on the well known $U_1\sim({\bf3},{\bf1})_{2/3}$ vector LQ solution as well as the GUT-inspired scalar LQ sol…
Supersymmetry is perhaps most effectively probed at the Tevatron through production and decay of weak gauginos. Most of the analyses of weak gaugino observables require electrons or muons in the final state. However, it is possible that the gauginos will decay primarily to tau leptons, thus complicating the search for supersymmetry. The motivating reasons for high tau multiplicity final states are discussed in three approaches to supersymmetry model building: minimal supergravity, gauge mediated supersymmetry breaking, and more minimal supersymmetry. The concept of ``e/mu/tau candidate'' is in…
Motivated by models proposed to explain the Standard Model anomalies, and the unprecedented $τ^{+}τ^{-}$ data to be collected by the Belle~II experiment during the next years, we study the kinematics of tau pair decays and propose a new method to search for lepton flavor violating processes in tau lepton decays to invisible beyond Standard Model particles, such as $τ\to \ell α$, where $\ell$ is either an electron or a muon, and $α$ is a massive particle that escapes undetected. The new method improves by one order of magnitude the expected upper limit on the $τ\to \ell α$ production in 3x1 pro…
We consider chargino-neutralino production, $\tildeχ_2^0 \tildeχ_1^\pm \to (h \tildeχ_1^0)(W^\pm \tildeχ_1^0)$, which results in Higgs boson final states that subsequently decay (inclusively) to leptons (either $h\rightarrow τ^+τ^-$ or $h\rightarrow W^+W^- \to (e^+e^-, μ^+μ^-, τ^+τ^-)+E_T^\mathrm{miss}$). Such channels are dominant in large regions of the allowed supersymmetric parameter space for many concrete supersymmetric models. The existence of leptons allows for good control over the backgrounds, rendering this channel competitive to the conventional $h\rightarrow b\bar{b}$ channel that…
I review recent estimates of the non-perturbative hadronic vacuum polarization contributions. Since these at present can only be evaluated in terms of experimental data of limited precision, the related uncertainties pose a serious limitation in our ability to make precise predictions. Besides e+e- - annihilation data also tau decay spectra can help to get better predictions. Here, it is important to account for all possible iso-spin violations in tau - decay spectra, from which e+e- cross sections may be obtained by an iso-spin rotation. The observed 10% discrepancy in the region above the rh…
We systematically investigate the prospects of testing new physics with tau sensitive near detectors at neutrino oscillation facilities. For neutrino beams from pion decay, from the decay of radiative ions, as well as from the decays of muons in a storage ring at a neutrino factory, we discuss which effective operators can lead to new physics effects. Furthermore, we discuss the present bounds on such operators set by other experimental data currently available. For operators with two leptons and two quarks we present the first complete analysis including all relevant operators simultaneously …
We report on the recent results of searches for lepton-flavor-violating tau decays as well as lepton-number-violating B decays with the world-highest data samples accumulated at the Belle.
In bilinear R-Parity violating models where a term ε_3L_3H_2 is introduced in the superpotential, the tau lepton can mix with charginos. We show that this mixing is fully compatible with LEP1 precision measurements of the Zττand Wτν_τcouplings even for large values of ε_3 and of the induced vacuum expectation value v_3 of the tau-sneutrino. The single production of charginos at e+e- colliders is possible in this case and we present numerical values of the cross-section at LEP1, LEP2 and an NLC. We find maximum values of 10 pb at LEP1 and 1 fb at NLC, while the corresponding values at LEP2 are …
A light pseudo-scalar that is copiously produced at the LHC may still be allowed by present searches. While masses above 65 GeV are effectively covered by di-photon searches, the lower mass window can be tested by a new search for boosted di-tau resonances. We test this strategy on a set of composite Higgs models with top partial compositeness, where most models can be probed with an integrated luminosity below 300 fb$^{-1}$.
We review the four-loop QED corrections to the anomalous magnetic moment of the muon. The fermionic contributions with closed electron and tau contributions are discussed. Furthermore, we report on a new independent calculation of the universal four-loop contribution and compare with existing results.
I calculate the QED coupling, alpha, directly in the MS-bar scheme using an unsubtracted dispersion relation for the three light quarks, and perturbative QCD for charm and bottom quarks. Compact analytical expressions are presented, making this approach particularly suitable for electroweak fits. After alpha^(-1) (m_tau) = 133.513 +- 0.025 is obtained in a first step, I perform a 4-loop renormalization group evolution with 3-loop matching conditions to arrive at alpha^(-1) (M_Z) = 127.934 +- 0.026 for alpha_s (M_Z) = 0.120. The corresponding hadronic contribution to the on-shell coupling is De…
We investigate the dipole moments of the tau- neutrino at high-energy and high luminosity at linear electron positron colliders, such as CLIC or ILC through the analysis of the reaction $e^{+}\, e^{-}\rightarrow ν\, \bar ν\,γ$ in the framework of the $SU(4)_L \times U(1)_X$ model. The limits on dipole moment were obtained for integrated luminosity of $\cal{L}$= 500-2000\, fb$^{-1}$ and center of mass between 0.5 and 3.0 TeV. The estimated limits for the tau-neutrino magnetic and electric dipole moments are improved by 2-3 orders of magnitude and complement previous studies on the dipole moment…
We investigate the bounds on tau-mu lepton flavor violation (LFV). Our main focus is on the collider constrains on tau-mu LFV. We use the Type-III Two-Higgs-Doublet-Model (2HDM) as a set up for our study. While the LFV branching fraction of the 125 GeV is well constrained by current LHC searches, the heavier neutral states could have a large branching fraction to tau and muon. We estimate the LHC reach for the 13 TeV center of mass energy with 300 $\text{fb}^{-1}$ luminosity for a neutral boson decaying into a tau and a muon. We identify parts of the LFV parameter space where the searches for …
LHC searches for the standard model Higgs Boson in di-photon or di-tau decay modes place strong constraints on the light top-pion state predicted in technicolor models that include colored technifermions. Compared with the standard Higgs Boson, the top-pions have an enhanced production rate (largely because the technipion decay constant is smaller than the weak scale) and also enhanced branching ratios into di-photon and di-tau final states (largely due to the suppression of WW decays of the technipions). These factors combine to make the technipions more visible in both channels than a standa…
Current results of the MiniBooNE experiment show excess events that indicate neutrino oscillations, but only if one goes beyond the standard 3 family scenario. Recently a different explanation of the events has been given, not in terms of oscillations but by the production and decay of a massive sterile neutrino with large transition magnetic moment. We study the effect of such a sterile neutrino in the rare decays $τ^- \rightarrow μ^- μ^+ π^- ν$ and $τ^{-}\rightarrow μ^{-} μ^{+} e^{-} νν$. We find that searches for these decays featuring displaced vertices between the $μ^-$ and the other char…
The singly charged $SU(2)_L$ singlet scalar, with its necessarily flavour violating couplings to leptons, lends itself particularly well for an explanation of the Cabibbo Angle Anomaly and of hints for lepton flavour universality violation in $τ\to μ\bar νν$. In a setup addressing both anomalies, we predict loop-induced effects in $τ\to eγ$ and in $τ\to eμμ$. A recast of ATLAS selectron and smuon searches allows us to derive a coupling-independent lower limit of $\approx 200$ GeV on the mass of the singly charged singlet scalar. At a future $e^+e^-$ collider, dark matter mono-photon searches c…
We review the Standard Model prediction of the tau lepton g-2 presenting updated QED and electroweak contributions, as well as recent determinations of the leading-order hadronic term, based on the low energy e+e- data, and of the hadronic light-by-light one.
We evaluate the O(alpha) QED corrections to the recoil electron energy spectrum in the process nu_l + e --> nu_l + e (+gamma), where (+gamma) indicates the possible emission of a photon and l=e, mu or tau. The soft and hard bremsstrahlung differential cross sections are computed for an arbitrary value of the photon energy threshold. We also study the O(alpha) QED corrections to the differential cross section with respect to the total combined energy of the recoil electron and a possible accompanying photon. Their difference from the corrections to the electron spectrum is investigated. We disc…
This article reviews and updates the Standard Model prediction of the tau lepton g-2. Updated QED and electroweak contributions are presented, together with new values of the leading-order hadronic term, based on the recent low energy e+ e- data from BaBar, CMD-2, KLOE and SND, and of the hadronic light-by-light contribution. The total prediction is confronted to the available experimental bounds on the tau lepton anomaly, and prospects for its future measurements are briefly discussed.
Results of searches for SUSY production at CMS in events with third-generation signatures are presented. Along with missing energy, the final states may include hadronic jets with or without b-quark tag, light leptons, and tau leptons. These features serve both to distinguish standard-model components, and sensitivity to those SUSY models that lead to final states rich of heavy-flavored particles.
Heavy neutrinos at the TeV scale have been searched for at the LHC in the context of left-right models, under the assumption that they couple to the electron, the muon, or both. We show that current searches are also sensitive to heavy neutrinos coupling predominantly to the tau lepton, and present limits can significantly constrain the parameter space of general flavour mixing.
LHC searches for non-standard Higgs bosons decaying into tau lepton pairs constitute a sensitive experimental probe for physics beyond the Standard Model (BSM), such as Supersymmetry (SUSY). Recently, the limits obtained from these searches have been presented by the CMS collaboration in a nearly model-independent fashion - as a narrow resonance model - based on the full 8 TeV dataset. In addition to publishing a 95% C.L. exclusion limit, the full likelihood information for the narrow resonance model has been released. This provides valuable information that can be incorporated into global BSM…
Magnetic and Rayleigh dark matter are models describing weak interactions of dark matter with electromagnetism through non-renormalizable operators of dimensions 5 and 7, respectively. Such operators motivate the existence of heavier states that couple to dark matter and are also charged under the electroweak interactions. The recent hints of a gamma-ray line in the Fermi data suggest that these states may be light enough to be produced at the LHC. We categorize such states according to their charges and decay modes, and we examine the corresponding LHC phenomenology. We emphasize unconstraine…
The $τ$ polarization can be easily measured at LHC in the 1-prong hadronic $τ$ decay channel by measuring what fraction of the $τ$-jet momentum is carried by the charged track. A simple cut requiring this fraction to be >0.8 retains most of the polarization of $τ=$+1 $τ$-jet signal while suppressing the polarization of $τ=$-1 $τ$-jet background and practically eliminating the fake $τ$ background. This can be utilized to extract the charged Higgs signal. It can be also utilized to extract the SUSY signal in the stau NLSP region, and in particular the stau co-annihilaton region.
In phenomenological preparation for new measurements one searches for the carriers of quality signatures. Often, the first approach quantities may be difficult to measure or to provide sufficiently precise predictions for comparisons. Complexity of necessary details grow with precision. To achieve the goal one can not break the theory principles, and take into account effects which could be ignored earlier. Mixed approach where dominant effects are taken into account with intuitive even simplistic approach was developed. Non dominant corrections were controlled with the help of Monte Carlo sim…
We confront the ATLAS and CMS new physics searches with simplified models from R-parity violating (RPV) supersymmetry that contain naturally light stops and higgsinos. We emphasize the important role played by searches for exotic heavy quarks and leptoquarks and discuss how these searches could be modified to better address RPV scenarios. We also argue that it would be useful to design searches for new physics based on the ttbar cross section measurements, to enhance searches for taus + jets + MET with regions with b tagging and reduced MET requirements, and to expand the search program for al…
Istituto Nazionale di Fisica Nucleare, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；PRISMA ++ Cluster of Excellence & Mainz Institute for Theoretical Physics Johannes Gutenberg University（约翰内斯·古腾堡大学）；Department of Physics & LEPP, Cornell University（康奈尔大学）
It is now a firmly established fact that all family lepton numbers are violated in Nature. In this paper we discuss the implications of this observation for future searches for rare tau decays in the supersymmetric see-saw model. Using the two loop renormalization group evolution of the soft terms and the Yukawa couplings we show that there exists a lower bound on the rate of the rare process mu --> e gamma of the form BR(mu --> e gamma) > C BR(tau --> mu gamma) BR(tau --> e gamma), where C is a constant that depends on supersymmetric parameters. Our only assumption is the absence of cancellat…
Final states involving tau leptons are important components of searches for new particles at the Large Hadron Collider (LHC). A proper treatment of tau spin effects in the Monte Carlo (MC) simulations is important for understanding the detector acceptance as well as for the measurements of tau polarization and tau spin correlations. In this note we present a TauSpinner package designed to simulate the spin effects. It relies on the availability of the four-momenta of the taus and their decay products in the analyzed data. The flavor and the four-momentum of the boson decaying to the tau-tau+ o…
The precise knowledge of the onset of the cross section $σ(e^+e^- \to τ^+τ^-)$ at the threshold is necessary for improving the accuracy of determination of the $τ$ mass from the threshold measurements. The QED radiative corrections of relative order $α$ and $α^2$, additional to the well known Coulomb factor, are considered in the threshold region. The correction terms of order $α^2$ are calculated, which contain coefficients enhanced by large parameters. As a result it is argued that the known $O(α)$ corrections provide the accuracy of the description of the cross section close to $10^{-4}$, r…
It is well known that in every experiment involving charged particles there are individual photons emitted with small energy /omega and those with /omega < /omega_{0} will not be detected but are present in the data. The typical procedure to estimate this effect consists in taking the leading logarithm from the soft photon approximation and to make a simulation through a Monte Carlo Algorithm (PHOTOS). The aim of this work is to compute the model independent QED correction to tau--> K /pi /nu and to estimate its effect in the decay width in the particular process tau^{+}-->K^{0} /pi^{+}/nu.
Understanding and identifying ditau jets -- jets consisting of pairs of tau particles, can be of crucial importance and may even turn out to be a necessity if the Higgs boson decays dominantly to new light scalars which, on the other hand, decay to tau pairs. As often seen in various models of BSM such as in the NMSSM, Higgs portals etc., the lightness of these new states ensures their large transverse momenta and, as a consequence, the collinearity of their decay products. We show that the non-standard signatures of these objects, which can easily be missed by standard analysis techniques, ca…
We re-analyze the results of the searches for Heavy Neutral Leptons (HNLs) by the CHARM experiment. We study HNL decay channel $N\to e^{+}e^{-}ν/μ^{+}μ^{-}ν$ and show that, in addition to the constraints on the HNL's mixings with $ν_e$ or $ν_μ$, the same data also implies limits on the HNLs that mix only with $ν_τ$ and have masses in the range $380 \text{ MeV}<m_{N}\lesssim 1.6\text{ GeV}$ - the region in the parameter space that was considered in the literature as a target for HNLs searches.
Pair production of tau leptons in two photon collision ${γγ\to τ^{+}τ}^{-}$ is studied at CLIC to test CP violating QED couplings of tau leptons. CP violating effects are investigated using tau pair spin correlations which are observed through the hadronic decay of each $τ$ into $πν$. Competitive bounds with previous works on the electric dipole moment from CP odd terms have been obtained.
We estimate that the LHC could set bounds BR(Z -> mu^\pm e^\mp) < 4.1 * 10^{-7} and BR(Z -> tau^\pm mu^\mp)< 3.5 * 10^{-6} (at 95% C.L.) with 20 inverse fb of data at 8 TeV. A similar sensitivity can be anticipated for Z -> tau^\pm e^\mp, because we consider leptonic tau decays such that Z -> tau^+ mu^- gives e^+ μ^- +$ invisibles. These limits can be compared to the LEP1 bounds of order 10^{-5} to 10^{-6}. Such collider searches are sensitive to a flavour-changing effective Z coupling which is energy dependent, so are complementary to bounds obtained from tau to 3mu and mu to 3e.
We present a reinterpretation of CMS searches for type-III seesaw lepton triplets at the LHC, both for the normal and the inverse seesaw. We find that, in contrast with previous expectations, these searches in the trilepton final state have a good sensitivity to triplets with predominant coupling to the tau lepton. We also show that the limits resulting from direct searches can be neatly presented for arbitrary masses and general flavour mixings. Thus, it turns out that the common (and often unrealistic) simplifying assumptions about the flavour couplings of the triplets used by experimental c…
Since the discovery of the Higgs boson in the year 2012, the CMS experiment continuously makes use of a variety of final states to measure the properties of the Higgs boson, as well as to search for it in final states where the discovery could not yet be established. This article concentrates on Higgs searches in fermionic final states including a search for the Standard Model Higgs boson in the $H \rightarrow b\overline{b}$ channel. Furthermore, three different searches for Higgs bosons beyond the Standard Model are presented. These comprise two searches for heavy neutral Higgs bosons and one…
We study the implications of the searches based on H -> tau^+ tau^- by the ATLAS and CMS collaborations on the parameter space of the two Higgs doublet model (2HDM). In the 2HDM, the scalars can decay into a tau pair with a branching ratio larger than the SM one, leading to constraints on the 2HDM parameter space. We have also discussed the implications for the 2HDM of the recent di-muon search by the ATLAS collaboration for a CP-odd scalar in the mass range 4-12 GeV.
The main goal of the IceCube Deep Core Array is to search for neutrinos of astrophysical origins. Atmospheric neutrinos are commonly considered as a background for these searches. We show here that cascade measurements in the Ice Cube Deep Core Array can provide strong evidence for tau neutrino appearance in atmospheric neutrino oscillations. A careful study of these tau neutrinos is crucial, since they constitute an irreducible background for astrophysical neutrino detection.
Theoretical predictions for the decay width of Standard Model Higgs boson into bottom quarks and tau-leptons, in the case when M_H< 2M_W, are briefly reviewed. The effects of higher order perturbative QCD (up to alpha_s^4-level) and QED corrections are considered. The uncertainties of the decay width of Higgs boson into bb and tau+tau- are discussed.
The processes of muons (tau) and charged pions pairs production at electron-positron annihilation with first order radiative corrections are considered. The calculation results are presented assuming the energies of final particles (cms implied) to be not far significantly from threshold production. The invariant mass distributions for the muon (tau) and pion pairs are obtained both for the initial and final state radiation. Some analytical calculations are illustrated numerically. The pions were assumed to be point-like objects and scalar QED was applied for calculation. The QED radiative cor…
We analyze a displaced dilepton signal expected at the LHC for a tau left sneutrino as the lightest supersymmetric particle with a mass in the range $45$-$100$ GeV. The sneutrinos are pair produced via a virtual $W$, $Z$ or $γ$ in the $s$ channel and, given the large value of the tau Yukawa coupling, their decays into two dileptons or a dilepton plus missing transverse energy from neutrinos can be significant. The discussion is carried out in the $μν$SSM, where the presence of $R$-parity violating couplings involving right-handed neutrinos solves the $μ$ problem and can reproduce the neutrino …
The Higgs boson search has shifted from LEP2 to the Tevatron and will subsequently move to the LHC. Due to the different initial states, the Higgs production and decay channels relevant for Higgs boson searches were different at LEP2 to what they are at hadron colliders. We suggest new benchmark scenarios for the MSSM Higgs boson search at hadron colliders that exemplify the phenomenology of different parts of the MSSM parameter space. Besides the m_h^max scenario and the no-mixing scenario used in the LEP2 Higgs boson searches, we propose two new scenarios. In one the main production channel …
The status of Monte Carlo system for the simulation of tau-lepton production and decay in high-energy accelerator experiments is reviewed. Since previous tau-lepton conference in 2008 some practical modifications have been introduced: (i) For the TAUOLA Monte Carlo generator of tau-lepton decays, automated and simultaneous use of many versions of form-factors for the calculation of optional weights for fits was developped and checked to work in Belle and BaBar software environment. Work on alternative paramterizations of hadronic decays is advanced. (ii) the TAUOLA universal interface based on…
The semileptonic decay channel B -> D tau nu is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently the BaBar experiment reported the first observation of the exclusive semileptonic decay B -> D tau nu, finding an approximately 2-sigma disagreement with the Standard-Model prediction for the ratio R(D)=BR(B->D tau nu)/BR(B->D l nu), where l=e,mu. We compute this ratio of branching fractions using hadronic form factors computed in unquenched lattice QCD and obtain R(D) = 0.316(12)(7), where the errors are statistical and total systematic, respe…
The LHC enters era of the Standard Model Z-boson couplings precise measurements, to match precision of LEP. The calculations of electroweak (EW) corrections in the Monte Carlo generators become of relevance. Precise predictions of Z-boson production and decay require classes of QED/EW/QCD corrections, preferably in the manner which allows for separation from the QCD dynamics of the production. At LEP, calculations, genuine weak and lineshape corrections were introduced into electroweak form-factors and Improved Born Approximation. This was well suited for so-called doubly-deconvoluted observab…
