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Search for W'->tb resonances with left- and right-handed couplings to fermions
Abstract
We present a search for the production of a heavy gauge boson, W', that
decays to third-generation quarks, by the D0 Collaboration in ppbar collisions
at sqrt(s)= 1.96 TeV. We set 95% confidence level upper limits on the
production cross section times branching fraction. For the first time, we set
limits for arbitrary combinations of left- and right-handed couplings of the W'
boson to fermions. For couplings with the same strength as the standard model W
boson, we set the following limits for M(W') > m(nu_R): M(W')>863 GeV for
purely left-handed couplings, M(W')>885 GeV for purely right-handed couplings,
and M(W')>916 GeV if both left- and right-handed couplings are present. The
limit for right-handed couplings improves for M(W') < m(nu_R) to M(W')>890 GeV.
... Typically, search strategies concentrate on single top-like tb production through the s-channel, and use the invariant mass distribution of the tb system as a discriminant. The first W search with arbitrary couplings was performed by D0 using 2.3 fb −1 of data [236], and M W < 800 GeV with purely left-or right-handed couplings were excluded. CDF excluded M W < 900 GeV with purely right-handed couplings using 9.5 fb −1 of data as shown in Fig. 26(a), and provides the world's most stringent limits on W with M W < 600 GeV to date [237]. ...
... [237] at 95% CL are compared to theory predictions for a right-handed W boson with SM-like coupling strengths. The exclusion limits by D0 [236], ATLAS [238], and CMS [239] are also shown. (b) Observed and expected upper limits on σ Z ×B(Z → tt) of a narrow topcolor Z resonance [241] at 95% CL are compared to theory predictions as a function of M Z . ...
On the twentieth anniversary of the observation of the top quark, we trace
our understanding of this heaviest of all known particles from the prediction
of its existence, through the searches and discovery, to the current knowledge
of its production mechanisms and properties. We also discuss the central role
of the top quark in the Standard Model and the windows that it opens for
seeking new physics beyond the Standard Model.
... Additional searches for W 0 ! tb [268][269][270][271] show no hints of new physics (see Figs. 40(c) and 40(d)). ...
The Tevatron collider led the World energy frontier program in particle physics during the late 20th and early 21st centuries. During this exciting period the standard model of particle physics was in its final stages of development and the search for physics beyond the standard model became one of the main research topics. In this review article we summarize the design and performance of the Tevatron collider and its two detectors, CDF and D0, as well as their evolution. Highlights of the Tevatron scientific results are provided, including the discovery of the top quark and measurements of its properties, studies and discoveries of the particles containing heavy quarks, precision studies of the strong and electroweak forces, searches for beyond the standard model particles and interactions, as well as the hunt for the Higgs boson.
... The extra vector bosons usually have interactions similar to those of the SM gauge bosons and can mediate the same processes with SM particles. In this case non-trivial interference between the contributions, for example, of W and W ′ , to various processes [32][33][34][35][36][37] could influence the experimental observation of the latter and the exclusion limits for their masses [38][39][40][41]. Interference of W ′ , Z ′ and γ ′ with the SM bosons and with the rest of corresponding KK-towers coming from extra dimensions leads to certain changes in invariant mass and P t distributions [42,43]. ...
We discuss the specificity of the interactions of the electroweak gauge boson excitations in models with warped extra dimensions. In particular, we show that the couplings of the gauge boson excitations $W^{\prime}$, $Z^{\prime}$, and $\gamma^\prime$ to the SM gauge bosons treated as the zero modes of the 5D gauge fields are either exactly equal to zero or very much suppressed. In the former case, the three-particle and four-particle interaction Lagrangians of the SM gauge bosons and their lowest excitations are found explicitly. Meanwhile, the couplings of $W^{\prime}$, $Z^{\prime}$, and $\gamma^\prime$ to the SM fermions are non-zero allowing for their production and decays. These are the characteristic features of the gauge boson excitations in models with warped extra dimensions, which distinguish them from the gauge boson excitations in other models beyond the SM.
... The most stringent limits on a right-handed W ′ R with SM-like couplings in the decay mode W ′ R → tb are set by the CMS experiment and excludes a W ′ R boson mass below 1.85 TeV at 95% CL [68] using 5 fb −1 of data at 7 TeV. The W ′ R → tb decay channel has been also searched for at ATLAS [69] and at the Tevatron [70,71]. ...
Overview on top couplings measurements is presented, and the prospects of
future measurements are discussed. The coupling of top to the W boson can be
examined either by looking at the decay of the top quark or from single top
quark production. With the advent of high statistics top physics at the LHC and
at the high-luminosity LHC, the processes where the bosons (photon, Z and
Higgs) are produced in association with top quarks become accessible. The first
evidence on the coupling of the top quark to these particles will come from the
production rate.
Searches are presented for heavy gauge bosons decaying into a top and a bottom quark in data collected by the CMS experiment at \( \sqrt{s}=13 \) TeV that correspond to an integrated luminosity of 2.2 and 2.6 fb−1 in the leptonic and hadronic analyses, respectively. Two final states are analyzed, one containing a single electron, or muon, and missing transverse momentum, and the other containing multiple jets and no electrons or muons. No evidence is found for a right-handed W′ boson (W′R) and the combined analyses exclude at 95% confidence level W′R with masses below 2.4 TeV if \( {M}_{\mathrm{W}{\prime}_{\mathrm{R}}}\gg {M}_{\nu_{\mathrm{R}}} \) (mass of the right-handed neutrino), and below 2.6 TeV if \( {M}_{\mathrm{W}{\prime}_{\mathrm{R}}}<{M}_{\nu_{\mathrm{R}}} \). The results provide the most stringent limits for right-handed W′ bosons in the top and bottom quark decay channel.
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A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at \( \sqrt{s}=8 \) TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.
The charged current in Weak Interaction, mediated by the W-boson, is maximally parity violating in the Standard Model of particle physics. Studies of neutron decay are very suitable to get access to this property of the Standard Model due to the absence of a nuclear structure, compared with nuclear beta decay. High precision experiments in this field are intended to test the Standard Model and the extensions. In this thesis the first asymmetry measurement with the new neutron decay spectrometer Perkeo III is described. During a nine-month beamtime at the Institute Laue Langevin the beta-asymmetry A in the decay of free polarized neutrons was measured. For the first time, a pulsed neutron beam was used. This significantly improved the experimental systematics. The data analysis confirmed the clean systematics, resulting in new values and improved uncertainties on the beta-asymmetry A and the ratio of axialvector to vector coupling lambda. Compared to the current world average given by the Particle Data Group (PDG), the uncertainty of this measurement is smaller by a factor of 5.
Results are presented from a search for the production of a heavy gauge boson
W' decaying into a top and a bottom quark, using a data set collected by the
CMS experiment at sqrt(s)=8 TeV and corresponding to an integrated luminosity
of 19.5 inverse femtobarns. Various models of W'-boson production are studied
by allowing for an arbitrary combination of left- and right-handed couplings.
The analysis is based on the detection of events with a lepton (e, mu), jets,
and missing transverse energy in the final state. No evidence for W'-boson
production is found and 95% confidence level upper limits on the production
cross section times branching fraction are obtained. For W' bosons with purely
right-handed couplings, and for those with left-handed couplings assuming no
interference effects, the observed 95% confidence level limit is M(W')>2.05
TeV. For W' bosons with purely left-handed couplings, including interference
effects, the observed 95% confidence level limit is M(W')>1.84 TeV. The results
presented in this paper are the most stringent limits published to date.
We discuss the specificity of searches for hypothetical W′, Z′ and γ′ bosons at hadron colliders in single top quark and μ
+ν
μ
production and Drell-Yan processes assuming these particles to be the Kaluza-Klein excitations of the gauge bosons of the Standard Model. In this case any process mediated by W is also mediated by the whole KK tower of its excitations, whereas to the processes mediated by Z and γ there is not only a contribution from their KK towers, but also from that of the graviton. The contributions of the towers above W′, Z′ and γ′ and above the first excitation of the graviton are included with the help of effective four-fermion Lagrangians. We compute the cross-sections of these processes taking into account the contributions of the Standard Model gauge bosons, of their first KK modes and of the corresponding KK towers and discuss the impact of the interference between them. For pp-collisions at the LHC with the center of mass energy 14 TeV we found specific changes of the distribution tails due to the interference effects. Such a modification of distribution tails is characteristic for the processes mediated by particles coming from extra dimensions and should always be taken into account when looking for them.
We analyze the general phenomenology of neutrinoless double beta decay in the
minimal left-right symmetric model. We study under which conditions a New
Physics dominated neutrinoless double beta decay signal can be expected in the
future experiments. We show that the correlation among the different
contributions to the process, arising from the neutrino mass generation
mechanism, plays a very important role. One may infer wrong conclusions without
properly considering the correlation. We have found that, if no fine tuned
cancellation is involved in the light active neutrino contribution, a New
Physics signal can be expected mainly from the $W_R-W_R$ channel. An
interesting exception is the $W_L-W_R$ channel which can give a dominant
contribution to the process if the right-handed neutrino spectrum is
hierarchical with $M_1\lesssim$ MeV and $M_2,M_3\gtrsim$ GeV. We also discuss
if a New Physics signal in neutrinoless double beta decay experiments is
compatible with the existence of a successful Dark Matter candidate in the
left-right symmetric models. It turns out that, although it is not a generic
feature of the theory, it is still possible to accommodate such a signal with a
KeV sterile neutrino as Dark matter.
We study LHC Higgs signatures from the extended electroweak gauge symmetry
SU(2) x SU(2) x U(1). Under this gauge structure, we present an effective UV
completion of the 3-site moose model with ideal fermion delocalization, which
contains two neutral Higgs states (h, H) and three new gauge bosons (W', Z').
We study the unitarity, and reveal that the exact E^2 cancellation in the
longitudinal WW scattering amplitudes is achieved by the joint role of
exchanging both spin-1 new gauge bosons and spin-0 Higgs bosons. We identify
the lighter Higgs state h with mass 125GeV, and derive the unitarity bound on
the mass of heavier Higgs boson H. The parameter space of this model is highly
predictive. We study the production and decay signals of this 125GeV Higgs
boson h at the LHC. We demonstrate that the h Higgs boson can naturally have
enhanced signals in the diphoton channel $gg \to h \to\gamma\gamma$, while the
events rates in the reactions $gg \to h \to WW^*$ and $gg \to h \to ZZ^*$ are
generally suppressed relative to the SM expectation. Searching the h Higgs
boson via associated productions and vector boson fusions are also discussed
for our model. We further analyze the LHC signals of the heavier Higgs boson H
as a distinctive new physics discriminator from the SM. For wide mass-ranges of
H, we derive constraints from the existing LHC searches, and study the
discovery potential of H at the LHC(8TeV) and LHC(14TeV).
We study the implications of the latest LHC searches for resonances in the
di-jet and di-boson final states and for quark compositeness in the di-jet
angular distributions on an iso-singlet W' with unit hypercharge. Predictions
presented in previous papers are collected and updated to take into account all
the present bounds from direct searches. It turns out that bounds on the
coupling to quarks coming from the LHC measurements of di-jet angular
distributions are starting to be competitive with the ones coming from direct
searches in the di-jet invariant mass spectrum. Moreover, the stringent bounds
on the mixing angle coming from the new searches in the $WZ\to l^{+}l^{-}l\nu$
final state, imply, in the case of discovery, the necessity to go to the LHC
with $\sqrt{s}=14$ TeV to be able to probe interesting masses and couplings
relevant for the W' decay into the W\gamma\ final state, particularly relevant
to get more insight on the nature of the new vector.
An iso-singlet W' carrying hypercharge one is considered within an effective
Lagrangian approach. The predictions for the exclusion in the (M_{W'},g_q/g)
parameter space presented in Ref. [1] for the search in the di-jet invariant
mass spectrum are shown to be in reasonable agreement with the LHC results
based on 1 fb^{-1} of integrated luminosity.
Enari, 17 H. Evans, 51 A. Evdokimov, 70 V.N. Evdokimov, 38 G. Facini, 59 T. Ferbel, 68 F. Fiedler, 24 F. Filthaut
- D Elvira
D. Elvira, 47 Y. Enari, 17 H. Evans, 51 A. Evdokimov, 70 V.N. Evdokimov, 38 G. Facini, 59 T. Ferbel, 68 F. Fiedler, 24
F. Filthaut, 34 W. Fisher, 61 H.E. Fisk, 47 M. Fortner, 49 H. Fox, 41 S. Fuess, 47 T. Gadfort, 70 A. Garcia-Bellido, 68
Ripp-Baudot, 19 F. Rizatdinova, 73 M. Rominsky, 47 C. Royon, 18 P. Rubinov, 47 R
- Rijssenbeek
Rijssenbeek, 69 I. Ripp-Baudot, 19 F. Rizatdinova, 73 M. Rominsky, 47 C. Royon, 18 P. Rubinov, 47 R. Ruchti, 53
G. Safronov, 36 G. Sajot, 14 A. Sánchez-Hernández, 32 M.P. Sanders, 25 B. Sanghi, 47 A.S. Santos, 5 G. Savage, 47
); DAE and DST (India); Colciencias (Colombia)
- Faperj Cnpq
- Fundunesp Fapesp
CNPq, FAPERJ,
FAPESP and FUNDUNESP (Brazil); DAE and DST
(India); Colciencias (Colombia);
- T Appelquist
- H C Cheng
- B A Dobrescu
T. Appelquist, H. C. Cheng, and B. A. Dobrescu, Phys.
Rev. D 64, 035002 (2001).
- J C Pati
- A Salam
J. C. Pati and A. Salam, Phys. Rev. D 10, 275 (1974).
- E Boos
- V Bunichev
- L Dudko
- M Perfilov
E. Boos, V. Bunichev, L. Dudko, and M. Perfilov, Phys.
Lett. B 655, 245 (2007).
- J.-M Frere
- W W Repko
J.-M. Frere and W. W. Repko, Phys. Lett. B 254, 485
(1991).
- Z Sullivan
Z. Sullivan, Phys. Rev. D 66, 075011 (2002).
- T Cdf Collaboration
- Aaltonen
CDF Collaboration, T. Aaltonen et al., Phys. Rev. Lett.
103, 041801 (2009).
- E E Boos
E. E. Boos et al., Phys. Atom. Nucl. 69, 1317 (2006).
- Comphep Collaboration
- E Boos
CompHEP Collaboration, E.E Boos et al., Nucl. Instrum.
Methods Phys. Res., Sect A 534, 250 (2004).
- J Pumplin
J. Pumplin et al., J. High Energy Phys. 07, 012 (2002).
High Energy Phys. 05 (2006) 026. We used " pythia 6
- T Sjöstrand
- S Mrenna
- P Skands
T. Sjöstrand, S. Mrenna, and P. Skands, J. High Energy
Phys. 05 (2006) 026. We used " pythia 6.409 ".
- M L Mangano
M. L. Mangano et al., J. High Energy Phys. 07, 001
(2003).
- N Kidonakis
- R Vogt
N. Kidonakis, and R. Vogt, Phys. Rev. D 68, 114014
(2003);
- J M Campbell
- R K Ellis
- R Hamberg
- W L Van Neerven
- W B Kilgore
J.M. Campbell, and R.K. Ellis, Phys. Rev. D 65,
113007 (2002); R. Hamberg, W.L. van Neerven, and
W.B. Kilgore, Nucl. Phys. B359, 343 (1991) and erratum
in B644, 403 (2002).
- N Kidonakis
N. Kidonakis, Phys. Rev. D 74, 114012 (2006).