Measurement of the B − lifetime using a simulation free approach for trigger bias correction
Not Available
Aaltonen, T.↗
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Results for “CDF”
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Transverse momentum distributions from effective field theory with numerical results
Not Available
Mantry, Sonny↗
Uncertainties on exclusive diffractive Higgs boson and jet production at the LHC
Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hernandez, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Top quark forward-backward asymmetry in the large invariant mass region
The forward-backward asymmetry in top-pair production that was observed in 2008 gets a boost in a recent CDF publication. Not only has the forward-backward asymmetry been further confirmed, but also distributional preferences are shown. Strikingly, the forward-backward asymmetry is the most sizable in the large M{sub tt} invariant mass region and in the large rapidity difference |{Delta}y| region. Here we used our previously proposed t-channel exchanged W{sup '} boson to explain the new observations. We show that a new particle exchanged in the t channel generically gives rise to such observations. Furthermore, we show that the proposed W{sup '} can be directly produced in association with a top quark at the Tevatron and the LHC. We perform a signal-background analysis and show that such a W{sup '} is readily observed at the Tevatron with a 10 fb{sup -1} luminosity and at the LHC-7 with just a 100 pb{sup -1} luminosity.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
QCD corrections to top quark pair production in association with a photon at hadron colliders
We compute QCD corrections to the production of a tt pair in association with a hard photon at the Tevatron and the LHC. This process allows a direct measurement of the top quark electromagnetic couplings that, at the moment, are only loosely constrained. We include top quark decays, treating them in the narrow width approximation, and retain spin correlations of final-state particles. Photon radiation off top quark decay products is included in our calculation and yields a significant contribution to the cross section. We study next-to-leading-order QCD corrections to the pp{yields}tt{gamma} process at the Tevatron for the selection criteria used in a recent measurement by the CDF collaboration. We also discuss the impact of QCD corrections to the pp{yields}tt{gamma} process on the measurement of the top quark electric charge at the 14 TeV LHC.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Top quark forward-backward asymmetry at the Tevatron and its implications at the LHC
The measurement of forward-backward asymmetry in the top and antitop quark (tt) production has been recently reconfirmed by the CDF Collaboration and shows a more than 3{sigma} deviation from the standard model prediction in the large tt invariant mass region. Models with new W{sup '} or Z{sup '} bosons have been invoked to explain this deviation. In the context of these models we perform a {chi}{sup 2} analysis with all the available experimental numbers in different {Delta}Y and M{sub tt} bins. We show that for the Z{sup '} model the region of parameter space which explains the Tevatron asymmetry can be probed in the same sign top production channel by Tevatron itself. Moreover, we consider a recently proposed observable, the one-sided forward-backward asymmetry (A{sub OFB}) at the LHC and conclude that both the W{sup '} and Z{sup '} models can lead to sizable A{sub OFB} even at the LHC running at a center of mass energy of 7 TeV for the model parameters consistent with the Tevatron measurements.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Studying of B{sub s}{sup 0}-B{sub s}{sup 0} mixing and B{sub s}{yields}K{sup (*)-}K{sup (*)+} decays within supersymmetry
Recent results from CDF and D0 collaborations favor a large CP asymmetry in B{sub s}{sup 0}-B{sub s}{sup 0} mixing, while the standard model prediction is very small. Such a large phase may imply sizable new physics effects in B{sub s}{sup 0}-B{sub s}{sup 0} mixing. We compute the gluino-mediated supersymmetry contributions to B{sub s}{sup 0}-B{sub s}{sup 0} mixing, B{sub s}{yields}K{sup (*)-}K{sup (*)+} and B{yields}X{sub s{gamma}} decays in the frame of the mass insertion approximation. Combining the constraints of {Delta}M{sub s},{Delta}{Gamma}{sub s},{phi}{sub s}{sup J}/{psi}{phi}, B(B{sub s}{yields}K{sup -}K{sup +}) and B(B{yields}X{sub s{gamma}}), we find that the effects of the constrained LL and RR insertions in B{sub s}{yields}K{sup (*)-}K{sup (*)+} decays are small because of the absence of gluino mass enhancement. For m{sub g}-tilde{sup 2}/m{sub q}-tilde{sup 2}=9, the constrained LR insertion can provide sizable contributions to all observables of B{sub s}{yields}K{sup (*)-}K{sup (*)+} decays except A{sub CP}{sup dir}(B{sub s}{yields}K{sup -}K{sup +}), and many observables are sensitive to the modulus and the phase of the LR insertion parameter. Near future experiments at Fermilab Tevatron and CERN LHC-b can test these predictions and shrink/reveal the mass insertion parameter spaces.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Evidence for a mass dependent forward-backward asymmetry in top quark pair production
Not Available
Aaltonen, T.↗
Measurement of event shapes in pp̄ collisions at √s=1.96 TeV
A study of event-shape observables in proton-antiproton collisions at √s=1.96 TeV is presented. The data for this analysis were recorded by the CDF II Detector at the Tevatron Collider. The variables studied are the transverse thrust and thrust minor, both defined in the plane perpendicular to the beam direction. The observables are measured using energies from unclustered calorimeter cells. In addition to studies of the differential distributions, we present the dependence of event-shape mean values on the leading-jet transverse energy. Data are compared with pythia Tune A and to resummed parton-level predictions that were matched to fixed-order results at next-to-leading-order (NLO) accuracy (NLO+NLL). Predictions from pythia Tune A agree fairly well with the data. However, the underlying event contributes significantly to these observables, making it difficult to make direct comparisons to the NLO+NLL predictions, which do not account for the underlying event. To overcome this difficulty, we introduce a new observable, a weighted difference of the mean values of the thrust and thrust minor, which is less sensitive to the underlying event, allowing for a comparison with NLO+NLL. Both pythia Tune A and the NLO+NLL calculations agree well within the 20% theoretical uncertainty with the data for this observable, indicating that perturbative QCD successfully describes shapes of the hadronic final states.
Aaltonen, T.↗
Evidence for tty Production and Measurement of (σ tt )γ/(σ tt )
Using data corresponding to 6.0 fb -1 of pp collisions at √s = 1.96 TeV collected by the CDF II detector, we present a cross section measurement of top-quark pair production with an additional radiated photon, ttγ. The events are selected by looking for a lepton (ell), a photon (γ), significant transverse momentum imbalance (E T ), large total transverse energy, and three or more jets, with at least one identified as containing a b quark (b). The ttγ sample requires the photon to have 10 GeV or more of transverse energy, and to be in the central region. Using an event selection optimized for the ttγ candidate sample we measure the production cross section of tt (σ tt ), and the ratio of cross sections of the two samples. Control samples in the dilepton+photon and lepton+photon+E T , channels are constructed to aid in decay product identification and background measurements. We observe 30 ttγ candidate events compared to the standard model expectation of 26.9 ± 3.4 events. We measure the ttγ cross section (σ tt ) to be 0.18 ± 0.08 pb, and the ratio of σ tt γ to σ tt to be 0.024 ± 0.009. Assuming no tty production, we observe a probability of 0.0015 of the background events alone producing 30 events or more, corresponding to 3.0 standard deviations.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Measurement of the cross section for prompt isolated diphoton production in pp̄ collisions at √s=1.96 TeV
This article reports a measurement of the production cross section of prompt isolated photon pairs in proton-antiproton collisions at √s=1.96 TeV using the CDF II detector at the Fermilab Tevatron collider. The data correspond to an integrated luminosity of 5.36 fb⁻¹. The cross section is presented as a function of kinematic variables sensitive to the reaction mechanisms. The results are compared with three perturbative QCD calculations: (1) a leading-order parton shower Monte Carlo, (2) a fixed next-to-leading-order calculation and (3) a next-to-leading-order/next-to-next-to-leading-log resummed calculation. The comparisons show that, within their known limitations, all calculations predict the main features of the data, but no calculation adequately describes all aspects of the data.
Aaltonen, T.↗
Search for resonant production of t t ¯ decaying to jets in p p ¯ collisions at s = 1.96 TeV
Not Available
Aaltonen, T.↗
Single jet and prompt-photon inclusive production with multi-Regge kinematics: From Tevatron to LHC
We study single jet and prompt-photon inclusive hadroproduction with multi-Regge kinematics invoking the hypothesis of parton Reggeization in t-channel exchanges at high energy. In this approach, the leading contributions are due to the fusion of two Reggeized gluons into a Yang-Mills gluon and the annihilation of a Reggeized quark-antiquark pair into a photon, respectively. Adopting the Kimber-Martin-Ryskin and Bluemlein prescriptions to derive unintegrated gluon and quark distribution functions of the proton from their collinear counterparts, for which we use the Martin-Roberts-Stirling-Thorne set, we evaluate cross section distributions in transverse momentum (p{sub T}) and rapidity. Without adjusting any free parameters, we find good agreement with measurements by the CDF and D0 Collaborations at the Tevatron and by the ATLAS Collaboration at the LHC in the region 2p{sub T}/{radical}(S) < or approx. 0.1, where {radical}(S) is the hadronic c.m. energy.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗