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    top quark decay width calculation

    Neglecting terms of order m2 b/m 2 Top Physics Motivation: Tied strongly to new physics such as Higgs and super- symmetry Standard Model tests require accurate Standard Model predictions Experimental Status: Top Quark was discovered in 1995 at Fermilab by the CDF and D collaborations Only basic parameters are measured (e.g. The top quark is the heaviest known elementary particle, and it is often considered a window through which to search for new physics processes in particle physics. The measurement of the inclusive production cross-section of a top quarkantiquark pair is an important test of the theory of quantum chromodynamics (QCD).Calculations of the cross-section are performed at next-to-next-to-leading order (NNLO) including the resummation of soft gluon terms (NNLL) [2328], the main uncertainties 1.3 that the tt production cross section is sensitive to the top-quarks electric charge (Q t) and in particular to anomalous couplings of the top quark to the photon. The decay t!bWis by far the dominant one with the Standard Model (SM).

    Due to the large production cross-section, many of the top quark properties can be measured very precisely at the LHC. (i) Consider the decay of a top quark to a W+ boson and a b quark. da Liberdade 615, 1, 4710-251 Braga | +351 963 171 939 Higgs decay to fermions h0!ff (a) (3P.) The fully di erential computation of corrections to the top quark width at next-to-leading order was reported in recent years in Refs. While the magnitudes of the anomalous couplings remain below 1

    top-momenta) Leptonic observables are sensitive to t t spin-correlations. As in the decay of top quarks, both processes involve the W tb vertex and are therefore (tchannel) B (t W b) = 3.14+0.94 0.80 pb . Indeed almost all characteristics of the processes with top-quark can be calculated with high theoretical accuracy. With each W boson being able to decay into a lepton and neutrino or two quarks, this means that there are effectively three possible final states; Two leptons and two neutrinos, , known as the leptonic channel.Two quarks and two anti-quarks, q q, known as the hadronic channel.Finally there is a final state of a lepton, a neutrino, a quark and an anti-quark, q, known as the semi Does this ambiguity have an impact on the measurements of the top quark mass at a hadron collider with the current or ultimate precision? We investigate the magnitudes and phases of "anomalous" contributions to this vertex in a two-Higgs doublet and the minimal supersymmetric extension of the standard model, and in a top-color assisted technicolor (TC2) model. This makes the top quark the only quark whose prop-erties can be studied without the complications of disentan-gling As the experimental lower limit on the top mass continued to increase, however, Answer (1 of 2): Mesons with a top quark are very likely impossible. less than 10 19 metres. mass difference and the top quark decay width. We calculate the next-to-leading order (NLO) QCD corrections to J / associated with W + b production from top quark decay. Decay width The decay width of the top quark is the largest of all fermions, and any deviation from SM expectation might hint to non-SM decays. The threshold region of heavy quark production has always been an ideal laboratory for onium spectroscopy. 2. 175 GeV) Large mass prevents large statistics More and Calculate the matrix element for each of these decays. We discuss the cross section for the production of W-bosons in e + e annihilation including all O(x) radiative corrections and finite width effects. Detection of the top decay products 151 1. The most probable decay (via the weak force) is: top quark The decay width of top quark can be divided into two parts: where is a dimensionless cutoff for . Also, the very fact that, for example, a bottom quark in top decay (t ^This would not be the case in codes or calculations which instead neglect width effects and interference between top A very few recent results, probed only through the top quark decay vertices are presented here. The top quark, recently observed by CDF [1] and D0 [2], will be the focus of much experimental attention in coming years. Two-body decay of the top quark into a bottom-meson plus u,c-quark: 4-momentum conservation between B, b, and q implies that the top-decay W boson is quite offshell: m W m t (m q /m b) = 45 GeV. Away-side u,c quark carries p T m t /2 = 85 GeV, i.e. On the experimental side, the first direct experimental determination of the top-quark decay width was performed by the experiments at the Tevatron collider [47, 48]. Understanding single-top-quark productiona and jets. We allow for the top quarks to be off-shell, considering radiation in both the top production and 1. The threshold region of heavy quark production has always been an ideal laboratory for onium spectroscopy.

    This width is proportional to the square of the charge of the b quark (see Fig. In the Standard Model, theoretical calculations predict a value for the decay width of 1.32 GeV for a top- quark mass of 172.5 GeV.

    We consider top quark decay in the standard model effective field theory (SMEFT). Next-to-leading order corrections to Wt production and decay. We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark In fact they both employ the universality of infrared divergences and the knowledge of = g 2 m t 3 64 m W 2 ( 1 m W 2 m t 2) 2 ( 1 + 2 m W 2 m t 2) is obtained. Detection of electrons and muons 151 background calculation on Z1 jets 184 C. Lepton + jets 184 1. 1. 1. arXiv, hep-ph(0506289), 2005. y electron = Av. We shall see at the end of our computation that for a massless quark this diagram does not contribute. $=decay width (or rate)=h " Finite lifetime implies (through%E%th 2) an uncertainty in energy (mass) Invariant mass distribution is determined by the Matrix Element factor != ig ! Draw the Feynman b diagram for this decay and explain why t W+b is the only observed decay channel of the top Finally, A bstract We present numerical calculations of the partial width of the charged Higgs boson decay into a top quark, H $$ \overline{t} $$ t + b + X , and the partial width of the Since the calculation of the decay amplitude including the full dependence on Higgs-boson and top-quark mass is not possible at the moment, only an expansion in = M2 H /(4m2 t) can be obtained.

    The branching ratio equals Br(t Wb) = 1.3 105 that make As the experimental lower limit on the top mass continued to increase, however, physicists started worrying about the effect of the top quark decay width, which grows like rnf for mt > mb + MW [l].

    It was shown in Sec. We extract the total width of the top quark, (t), from the partial decay width (t Wb) measured using the t-channel cross section for single top-quark production and from the In the last 30 years much eort has been invested on the theoretical side to calculate the top-quark decay width with increasing precision within the SM.

    After having done this numerous times, I can not figure out how the result. Single-top-quark production and decay at NNLO. (i) Consider the decay of a top quark to a W+ boson and a b quark. In Section 2. we summarize SM precision calculations of the top quark mass relations and of the total top quark width. Compare this to the matrix element for muon decay, in Q4 above. CMS. According to the decays of two Single top quarks. This can happen in several ways (called channels): either an intermediate W-boson decays into a top and antibottom quark ("s-channel") or a bottom quark (probably created in a pair through the decay of a gluon) transforms to a top quark by exchanging a W-boson with an up or down quark ("t-channel"). the inclusive decay width, but the dierential decay rate is also of substantial interest, especially when consid-ering the measurement of top-quark mass [6] and elec-troweak (EW) couplings We present a measurement of the total decay width of the top quark using events with top-antitop-quark pair candidates reconstructed in the final state with one charged lepton 1. We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. The top quark, first observed at Fermilab in 1995, was the experimental evidence indicates they are no bigger than 10 4 times the size of a proton, i.e. This is a consequence of the high mass and rapid decay of the top quark - Before it has time to form a meson, it will decay. This process has the potential to be detected at the LHC. It, however, still suffered from large experimental uncertainties. We present the full set of analytical formulae and the corresponding numerical results for the decay width of the W-boson and the top quark. A large width would smear out res- The only exception is the top quark, which may decay before it hadronizes.

    The most recent results are discussed in this review. 6.

    The total In many cases the narrow width approximation -in which unstable particles are treated on-shell, with the decay width neglected -does not provide the required precision. We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite These results are based on proton-proton collision datasets recorded by the ATLAS and CMS experiments at sqrt(s)=7, 8 and 13 TeV. 8.5 Interpretation of the results. Due to the very heavy top quark mass, this diagram generates a high enough decay rate that necessarily must be taken in consideration. We perform the numerical calculation by taking the LHM input parameters f = 3, 4 TeV and 0.1 < c < 0.6, and discuss the numerical results of the decay width up to the QCD NLO within the recent experimentally constrained LHM parameter space region. The data sample was collected by the ATLAS detector at the LHC in protonproton collisions at a centre-of-mass We then recall the importance of the top quark mass in EW precision measure-ments. The most precise theoretical calculation of the top-quark decay width includes NLO electroweak corrections and e ects of nite b-quark mass and nite Wboson mass on top of the NLO and NNLO QCD corrections [12]. To obtain the decay width, the combination A = AW + At is inserted into eq.

    decay width of top quark can be divided into two parts: where is a dimensionless cutoff for .Below we describe our method. " [4]. Top quark physics measurements require increasingly precise theoretical descriptions of top quark production and decay. Draw the Feynman b diagram for this decay and explain why t W+b is the only observed decay channel of the top quark.

    Sea quarks. New physics interactions can affect the strength and structure of the tbW vertex. We study gluon radiation in top quark production above threshold at high energy e + e - colliders. The electroweak corrections have been computed in Refs. The rst LO predictions for the semileptonic decay rate were calculated in Refs. In the standard model, the top quark decay width t is computed from the exclusive tbW decay. M( e e ) g2 w m2 W q2 M( ) g2 w m2 W q2 Same as for muon decay above!

    In the standard model the top decays to Wb with a branching fraction > 0.998 at 90% C.L., constrained by the unitarity of the three-generation CKM matrix. It will be important to test the Standard Model predictions for the width of the top quark as well as search for rare or non-standard decays which may give us a glimpse into post-Standard Model physics. With its correspondingly short it is more boosted than the W decay quarks in standard tbWbqq decays.

    The ATLAS Collaboration presented a new measurement of the

    of the top-quark decay width is therefore fundamental and it is the main goal of this thesis.

    The NNLO corrections

    Computing the decay width for Top quark decaying to bottom quark and W boson. The U.S. Department of Energy's Office of Scientific and Technical Information to calculate the NNLO corrections is similar to the q T subtraction method of Catani and Grazzini [16]. The U.S. Department of Energy's Office of Scientific and Technical Information This calculation is based on ref. (1) for the W and the top quark loop induced contributions. A. Standard-model top-quark decay modes 151 B. Subsequent decays of W bosons therefore define final states of the top-antitop event.

    Direct measurement of the total decay width of the top quark. The top quark mass is a renormalization scheme-dependent quantity. 47INFN Pavia, I-27100 Pavia, Italy 48University of Pavia, I-27100 Pavia, Italy 49University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA 50Purdue University, West Lafayette, Indiana

    Motivated by evidence that the top quark mass lies near the b WZ threshold, we compute the decay rate for t b WZ in the Standard Model, including the effects of the finite fore the top quark has a chance to form a hadronic bound state. All decays include a Higgs produced in association with a top quark pair, followed by a dimuon decay of the Higgs boson, t tH;H !

    This is because the transformation proceeds by the exchange of charged W bosons, which must change the charge by one unit. in the triangle loop, contribute to the decay width of. The branching ratio equals Br(t Wb) = 1.3 105 that make possible searches for this rare t-quark decay at LHC. The width for a value of m t = 173.3 GeV/c2 is 1.35 GeV/c2 (we use s(M Z) = 0.118) and increases with mass. .

    It will be important to test the Standard Model predictions for the In this work, we present the complete calculations of top quark decay width at NNLO in QCD, including NLO electroweak corrections as well as nite bottom quark mass and W boson width effects. Top quark width and branching fraction ratio Top quark has the largest decay width of the known fermions in the SM. We consider top quark decay in the Standard Model Effective Field Theory (SMEFT).We present a calculation of the total decay width and the W -boson helicity fractions at next-to In the narrow-width approximation for the top quark, NNLO QCD calculations for on-shell top quark production and top quark decay have been combined to allow for fully differential predictions . is sensitive to the top-quark decay width, Title: Top-Quark Decay at Next-to-Next-to-Leading Order in QCD Authors: Jun Gao , Chong Sheng Li , Hua Xing Zhu (Submitted on 10 Oct 2012 ( v1 ), last revised 22 Jan 2013 (this version, v3)) Direct Bound on the Total Decay Width of the Top Quark in ${{\mathit p}}{{\overline{\mathit p}}}$ Collisions at $\sqrt {s }$ = 1.96 TeV Except where otherwise noted, content of the 2022 Review of Particle Physics is licensed under a Creative Commons Attribution-NonCommercial 4.0 International ( CC BY-NC 4.0 ) license. The top quark mass is a renormalization scheme-dependent quantity. The data sample was collected by the ATLAS The decay widths are: There are three possible lepton channels e e, , , but only two quark channels ud 0and cs, because the top quark is too heavy for the W to decay to tb0. Every time I do this calculation, I find the reduced matrix element Can the total width of the top quark be measured in a model-independent way and to what precision? decay width of the top quark using tt events in the lep-ton+jets nal state. We argue in favor of using the three body decays tbfifj to compute t as a sum over these Expectations for observation of top quark pair production in the dilepton nal state with the rst 10 pb-1 of cms data.

    This can happen in several ways (called channels): either an intermediate W-boson decays into a top and antibottom quark ("s-channel") or a bottom quark (probably created in a pair through the decay of a gluon) transforms to a top quark by exchanging a W-boson with an up or down quark ("t-channel").

    The top-quark decay width depends on the top-quark mass (mt), the W boson mass (mW),the Fermicoupling constant(GF), the strongcoupling constant(s) andthemagnitudeofthetop-to-bottom-quarkcouplinginthequark-mixingmatrix (Vtb).2224 The most recent calculations at next-to-next-to leading order (NNLO) This paper is organized as follows: In We present a calculation of the total decay width and the W-boson helicity fractions at next-to the the top quark-Higgs Yukawa coupling and the top quark decay width. m t! 2 for the role of double-DIS scales and the relevancy for PDFs. The top quark interacts with gluons of the strong interaction and is typically produced in hadron colliders via this interaction. However, once produced, the top (or antitop) can decay only through the weak force. It decays to a W boson and either a bottom quark (most frequently), a strange quark, or, on the rarest of occasions, a down quark . We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark This process can be run by using Our results show that the decay width for process t J / + W + + b + X at the leading order is significantly enhanced by the NLO QCD corrections.

    ), with speci c emphasis on the fully-hadronic The recent next-to-next-to-leading-order (NNLO) calculation with QCD and electroweak corrections predicts top, the top quark decay width to be 1.32 GeV at top quark mass of M top = 172.5 GeV/c2 [3]. It is expected that the relation between tt and Q t Abstract. 10 In SM, the top quark almost exclusively decays into a W boson and b quark. Production and decay:Spin-correlation @ NNLO QCD Direct measurement of top-quark spin density matrix [CMS,PAS TOP-18-006] full spin information systematic di culties (neutrinos ! PACS: 12.38.-t, 14.54Ha J. Campbell and F. Tramontano.

    In Sect. The next-to-leading-order and next-to-next-to-leading-order calculation predicts NLO = 1:33 GeV, and NNLO = 1:322 GeV respectively [6]. Because almost all of the energy of the collision is the result of top and antitop decay, we simply add the energies of the four jets, the soft muon, the muon and the neutrino before dividing by the two tops (actually a top and an antitop quark) to obtain the mass of the most recently discovered quark. We consider top quark decay in the standard model effective field theory (SMEFT). Abstract We present numerical calculations of the partial width of the charged Higgs boson decay into a top quark, H $$ \\overline{t} $$ t + b + X, and the partial width of the top quark decay into a light charged Higgs boson t H+ + b + X at next-to-next-to-leading order (NNLO) in QCD, based on a factorization formula of the jet mass. (a) Fully leptonic decay (b) Semi-leptonic decay (c) Fully hadronic decay Figure 1: Feynman diagrams describing the signal decays included in the present analysis.

    1. However, if there are additional With a mass above the Wb threshold, and Vtbclose to unity, the decay width of the top quark is expected to be dominated by the two-body channel t Wb. The next-to-leading (NLO) QCD corrections to the top quark total decay width and many kine-matic distributions are known since long ago [1{3]. Because of this it is im-

    The calculation is presented in the form of corrections to the LO decay width value, (0) t, from Equation1.2 t = (0) 1 + (1) These contributions from the top quark triangle loop are computed approximately using a large quark mass expansions formula [14], and the corres- ponding exact calculations are also obtained [15]. We discuss, in particular, the role of EW precision measurements under the assumption that a SM Higgs boson has been discovered. We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. (3) proportional to the partial width (t W b). The most precise theoretical calculation of the top-quark decay width includes NLO electroweak corrections and e ects of nite b-quark mass and nite Wboson mass on top of the NLO and NNLO

    calculate top quark decay at NNLO level " Define , which measures the invariant mass of jet. Introduction . In the limit of #0, only soft radiations and (or) radiations collinear to the b quark are allowed.

    Introduction The physics of the top-quark is one the main areas of study in current high energy physics.

    arXiv, hep-ph(0408049), 2004. The calculation of the partial width of the rare t-quark decay into -meson, W -boson and b-quark (t Wb) is presented. The decay width of a particle (A) decaying to two nal state particles is given by = 1 2m A Z d 2jM(m A!p 1 + p 2)j2: (1) Show that for two nal state Keywords: top-quark, rare decay, charged Higgs 1. The top quark, recently observed by CDF [1] and D0 [2], will be the focus of much experimental attention in coming years.

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