Top quark production: Sensitivity to new physics

Hill, Christopher T.; Parke, Stephen J.

doi:10.1103/physrevd.49.4454

Cited by 300 publications

(366 citation statements)

References 21 publications

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“…This means that the tt must form a color octet, Lorentz vector state, so if there is a new particle in the schannel coupling to tops, it must be a heavy color octet vector boson. 1 Such a 'heavy gluon partner' G can arise in a wide variety of models [16], including top-color models [17,18], technicolor [19], warped extra dimensions [20,21], universal extra dimensions [22] and chiral color [23][24][25]. As we will discuss below, G particles are constrained by flavor physics and collider searches, although we disagree with some exclusion claims in the literature.…”

Section: Jhep03(2011)003mentioning

confidence: 80%

LHC predictions from a tevatron anomaly in the top quark forward-backward asymmetry

Bai

Hewett

Kaplan

et al. 2011

J. High Energ. Phys.

112

111

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Abstract:We examine the implications of the recent CDF measurement of the top-quark forward-backward asymmetry, focusing on a scenario with a new color octet vector boson at 1-3 TeV. We study several models, as well as a general effective field theory, and determine the parameter space which provides the best simultaneous fit to the CDF asymmetry, the Tevatron top pair production cross section, and the exclusion regions from LHC dijet resonance and contact interaction searches. Flavor constraints on these models are more subtle and less severe than the literature indicates. We find a large region of allowed parameter space at high axigluon mass and a smaller region at low mass; we match the latter to an SU(3) 1 × SU(3) 2 /SU(3) c coset model with a heavy vector-like fermion. Our scenario produces discoverable effects at the LHC with only 1 − 2 fb −1 of luminosity at √ s = 7 − 8 TeV. Lastly, we point out that a Tevatron measurement of the b-quark forwardbackward asymmetry would be very helpful in characterizing the physics underlying the top-quark asymmetry.

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Section: Jhep03(2011)003mentioning

confidence: 80%

LHC predictions from a tevatron anomaly in the top quark forward-backward asymmetry

Bai

Hewett

Kaplan

et al. 2011

J. High Energ. Phys.

112

111

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“…Recent theoretical calculations predict, for an assumed top quark mass (m t ) of 175 GeV, an inclusive top quark pair production cross section at s p 1:96 TeV of 6.7 pb with an uncertainty of less than 15% [4,5]. If the observed production cross section were to differ significantly from the standard model prediction, it would be evidence of new physics such as exotic top quark decays or new production mechanisms such as t t resonances [6]. Significant deviation among measured cross sections obtained from the observations of different top quark decay channels would also indicate the presence of new physics.…”

Section: A the Top Quarkmentioning

confidence: 99%

Measurement of thett¯production cross section inpp¯collisions using dilepton events

Abazov¹,

Abbott²,

Abolins³

et al. 2007

Phys. Rev. D

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We present a measurement of the t t pair production cross section in p p collisions at s p 1:96 TeV utilizing approximately 425 pb ÿ1 of data collected with the D0 detector. We consider decay channels containing two high p T charged leptons (either e or ) from leptonic decays of both top-daughter W bosons. These were gathered using four sets of selection criteria, three of which required that a pair of fully identified leptons (i.e., e , ee, or ) be found. The fourth approach imposed less restrictive criteria on one of the lepton candidates and required that at least one hadronic jet in each event be tagged as containing a b quark. For a top quark mass of 175 GeV, the measured cross section is 7:4 1:4 stat 1:0 syst pb and for the current Tevatron average top quark mass of 170.9 GeV, the resulting value of the cross section is 7:8 1:8 stat syst pb.

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“…In these models, the basic assumption is that new dynamics strong enough to form chiral condensates is effective for the third generation, which therefore is treated differently from the first two. As a consequence, TopColor models have peculiar implications for the phenomenology involving the third generation, such as top and bottom production [74] and the Z → bb decay rate [75]. In particular, they are expected to yield large effects in FCNC B decays involving third generation leptons [76,77].…”

Section: Topcolor Modelsmentioning

confidence: 99%

First limit on inclusive decay and constraints on new physics

1996

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In a recent article [1] we presented the derivation of the first limit on the inclusive B → X s νν decay rate. Our work stemmed from the observation that a published ALEPH bound on BR(B → τν) [2], inferred from the absence of large missing energy events in B decays, implies also a limit on BR(B → X s νν). We estimated this limit by comparing the missing energy spectra in the two decay modes. Theoretically, B → X s νν is a very clean process, which is also sensitive to several possible sources of new physics [1]. Therefore, a dedicated experimental search is important. The result of such an analysis by the ALEPH Collaboration, using the full LEP-I data sample, is to appear soon [3].As a result of discussions with members of the ALEPH Collaboration [4], we found two errors in our numerical results. The corrected analysis yields a limit weaker than our original result [1] by about a factor of three. The corrections included here are formally beyond the free quark decay result at tree level (of order α s , Λ QCD /m b , and higher). However, they affect the final limit significantly, due to the specific details of the experimental analysis.First, due to a mistake in our Monte Carlo code, the energy of the X s hadronic final state in the B rest frame was evaluated as a fraction of the b quark mass, rather than as a fraction of the B meson mass. This resulted in a harder missing energy spectrum than the true one. Correcting for this weakens the limit by about 35%.Second, we neglected the effects of the invariant mass distribution of the final hadrons, 1 which we (implicitly) assumed not to extend to high mass states. However, the invariant mass of the X s system can be well above 1 GeV [5]. Because of the large boost into the LEP laboratory frame and the high missing energy range (> 35 GeV) used in the analysis[2] (which is large compared to the average B meson energy at LEP), neglecting this effect yielded a missing energy spectrum in the laboratory frame considerably harder than the correct one.It is not straightforward to include properly this second effect into the analysis. However, an estimate can be obtained by approximating the invariant mass spectrum of the X s system with a Gaussian distribution with mean (µ) and variance (σ) fitted to the averages M 2 X and M 4 X , as given in [5]. Such a fit yields µ ≃ 1.35 GeV and σ ≃ 0.6 GeV. There is about a 10% uncertainty in these values, due to their dependences on the heavy quark effective theory parameterΛ (≃ m B − m b ). Treating the X s mass distribution as independent of the energy spectrum, and including a theoretical uncertainty of about 15% related to the fitted values of µ and σ, we find that the original limit given in [1] is weakened by about a factor of three. While small values of E X favor small values of M X (beyond the trivial kinematic constraint E X > M X ), the correlation between E X and M X only slightly improve the bound.In conclusion, the bound on BR(B → X s νν) given in the Abstract and in Eqs. (1.2) and (6.1) of [1] is weaker by about a facto...

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Top quark production: Sensitivity to new physics

Cited by 300 publications

References 21 publications

LHC predictions from a tevatron anomaly in the top quark forward-backward asymmetry

LHC predictions from a tevatron anomaly in the top quark forward-backward asymmetry

Measurement of thett¯production cross section inpp¯collisions using dilepton events

First limit on inclusive decay and constraints on new physics

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