arXiv subjects

T. Plehn

Publications and source records attributed to T. Plehn.

At least 55 records · Page 3Linked to original sources

arXiv2002

Stop Lepton Associated Production at Hadron Colliders

At hadron colliders, the search for R-parity violating supersymmetry can probe scalar masses beyond what is covered by pair production processes. We evaluate the next-to-leading order SUSY-QCD corrections to the associated stop or sbottom production with a lepton through R-parity violating interactions. We show that higher order corrections render the theoretical predictions more stable with respect to variations of the renormalization and factorization scales and that the total cross section is enhanced by a factor up to 70% at the Tevatron and 50% at the LHC. We investigate in detail how the heavy supersymmetric states decouple from the next-to-leading order process, which gives rise to a theory with an additional scalar leptoquark. In this scenario the inclusion of higher order QCD corrections increases the Tevatron reach on leptoquark masses by up to 40 GeV and the LHC reach by up to 200 GeV.

hep-ph↗

arXiv2002

Determining the Higgs Boson Self Coupling at Hadron Colliders

Inclusive Standard Model Higgs boson pair production at hadron colliders has the capability to determine the Higgs boson self-coupling, lambda. We present a detailed analysis of the gg\to HH\to (W^+W^-)(W^+W^-)\to (jjl^\pmν)(jj{l'}^\pmν) and gg\to HH\to (W^+W^-)(W^+W^-)\to (jjl^\pmν)({l'}^\pmν{l''}^\mpν) (l, {l'}, {l''}=e, μ) signal channels, and the relevant background processes, for the CERN Large Hadron Collider, and a future Very Large Hadron Collider operating at a center-of-mass energy of 200 TeV. We also derive quantitative sensitivity limits for lambda. We find that it should be possible at the LHC with design luminosity to establish that the Standard Model Higgs boson has a non-zero self-coupling and that lambda / lambda_{SM} can be restricted to a range of 0-3.8 at 95% confidence level (CL) if its mass is between 150 and 200 GeV. At a 200 TeV collider with an integrated luminosity of 300 fb^{-1}, lambda can be determined with an accuracy of 8 - 25% at 95% CL in the same mass range.

hep-ph↗

arXiv2001

Determining the Structure of Higgs Couplings at the LHC

Higgs boson production via weak boson fusion at the CERN Large Hadron Collider has the capability to determine the dominant CP nature of a Higgs boson, via the tensor structure of its coupling to weak bosons. This information is contained in the azimuthal angle distribution of the two outgoing forward tagging jets. The technique is independent of both the Higgs boson mass and the observed decay channel.

hep-ph↗

arXiv2001

VLHC Predictions for H to tau tau in Weak Boson Fusion

Higgs production in weak boson fusion with subsequent decay H to tau tau to e mu p_T_miss provides a means to measure Higgs Yukawa couplings and Higgs interactions to weak bosons. The potential precision of cross section measurements at a VLHC is investigated.

hep-ph↗

arXiv2001

Higgs Decays to Muons in Weak Boson Fusion

We investigate the muonic decay of a light Higgs boson, produced in weak boson fusion at future hadron colliders. We find that this decay mode would be observable at the CERN LHC only with an unreasonably large amount of data, while at a 200 TeV vLHC this process could be used to extract the muon Yukawa coupling to about the 10% level, or better if significant improvements in detector design can be achieved.

hep-ph↗

arXiv2001

CP-Violating Phases in SUSY, Electric Dipole Moments, and Linear Colliders

We reexamine large CP-violating phases in the general Minimal Supersymmetric Standard Model, as well as more restricted models. We perform a detailed scan over parameter space to find solutions which satisfy the current experimental limits on the electric dipole moments of the electron, neutron and $^{199}$Hg atom, exploring the allowed configurations of phases and masses, and we attempt to quantify the level of tuning of the parameters necessary to populate the regions of cancellations. We then consider the measurement of CP-violating phases at a future linear collider. We find that measurements of chargino and neutralino masses and production cross-sections allow for a determination of $ϕ_1$(the phase of $M_1$) to a precision of $π/30$, while the EDM constraints require that $θ_μ$ be too small to be measured. Using the EDM constraints we find that the CP-even model parameters and the phase $ϕ_1$ can be determined at a Linear Collider with $400 \gev$ c.m. energy. As long as some information on the size of $|μ|$ is included in the observables, a measurement of $ϕ_1$ is guaranteed for $ϕ_1 > π/10$. To unambiguously identify CP violation, we construct CP-odd kinematical variables at a linear collider. However, the CP asymmetries are rather small, typically about $0.1-1.5%$, and it will be challenging to experimentally observe the predicted asymmetries.

hep-ph↗

arXiv2000

H-->WW as the discovery mode for a light Higgs boson

The production cross section for a m_H=115 GeV, SM Higgs boson in weak boson fusion at the LHC is sizable. However, the branching fraction for H-->WW is expected to be relatively small. The signal, with its two forward jets, is sufficiently different from the main backgrounds that a signal to background ratio of better than 1:1 can nevertheless be obtained, with large enough rate to allow for a 5 sigma signal with 35 fb^{-1} of data. The H-->WW signal in weak boson fusion may thus prove to be the discovery mode for the Higgs boson at the LHC.

hep-ph↗

arXiv2000

Single Stop Production at Hadron Colliders

We analyze the production of a single top squark at hadron colliders: ppbar/pp -> \tilde{t}_1 + X. The total cross sections and the transverse momentum distributions are presented in next-to-leading order QCD. The higher-order corrections render the predictions theoretically stable with respect to variations of the factorization and renormalization scales. The transverse momentum distribution is resummed to estimate effects of the small transverse momentum regime on possible analyses. Since the corrections increase the cross sections and reduce the theoretical uncertainty, the discovery range for these particles is extended in the refined analysis.

hep-ph↗

arXiv2000

Parton Distributions Working Group

The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, we introduce a "Manifesto" that describes an optimal method for reporting data.

hep-ph↗

arXiv2000

Physics Potential of a Tevatron Tripler

We explore the capabilities for new physics discovery in proton-antiproton collisions at 5.4 TeV center-of-mass energy with luminosity $10^{33} cm^{-2} s^{-1}$ at a Tripler upgrade of the Tevatron collider. The prospects are robust for the usual Higgs boson and supersymmetry benchmarks. With an integrated luminosity of 40 fb$^{-1}$, discoveries at 5$σ$ could be made for a standard Higgs boson of mass $\alt 680$ GeV (600 GeV for 10 fb$^{-1}$), a lighter chargino of mass $\alt 380$ GeV, and an extra $Z$ boson of mass $\alt 2.6$ TeV; four-fermion contact interactions from new physics with scale $\alt 74$ TeV could be excluded at the 95% confidence level.

hep-ph↗

arXiv2000

Measuring CP Violating Phases at a Future Linear Collider

At a future Linear Collider one will be able to determine the masses of charginos and neutralinos and their pair production cross sections to high accuracies. We show how systematically including the cross sections into the analysis improves the measurement of the underlying mass parameters, including potential CP violating phases. In addition, we investigate how experimental errors will affect the determination of these parameters. We present a first estimate on the lower limit of observable small phases and on the accuracy in determining large phases.

hep-ph↗

arXiv2000

A method for identifying H -> tau tau -> e mu pTmiss at the CERN LHC

Weak boson fusion promises to be a copious source of intermediate mass Higgs bosons at the LHC. The additional very energetic forward jets in these events provide for powerful background suppression tools. We analyze the subsequent H -> tau tau -> e mu pTmiss decay for Higgs boson masses in the 100-150 GeV range. A parton level analysis of the dominant backgrounds demonstrates that this channel allows the observation of H -> tau tau in a low-background environment, yielding a significant Higgs boson signal with an integrated luminosity of order 60 fb^-1 or less, over most of the mass range. We also restate a No-Lose Theorem for observation of at least one of the CP-even neutral Higgs bosons in the MSSM, which requires an integrated luminosity of only 40 fb^-1.

hep-ph↗

arXiv1999

The Production of Charginos/Neutralinos and Sleptons at Hadron Colliders

We analyse the production of charginos/neutralinos and sleptons at the hadron colliders Tevatron and LHC in the direct channels: $p\bar{p}/pp \to \tildeχ_i \tildeχ_j + X$ and $\tilde{\ell} \bar{\tilde{\ell}'} +X$. The cross sections for these reactions are given in next-to-leading order SUSY QCD. By including the higher-order corrections, the predictions become theoretically stable, being nearly independent of the factorization and renormalization scales. Since the corrections increase the cross sections, the discovery range for these particles is extended in the refined analysis.

hep-ph↗

arXiv1999

SUSY Particle Production at the Tevatron

The calculation of the next-to-leading order SUSY-QCD corrections to the production of squarks, gluinos and gauginos at the Tevatron is reviewed. The NLO corrections stabilize the theoretical predictions of the various production cross sections significantly and lead to sizeable enhancements of the most relevant cross sections for scales near the average mass of the produced massive particles. We discuss the phenomenological consequences of the results on present and future experimental analyses.

hep-ph↗

arXiv1997

Stop Production at Hadron Colliders

Stop particles are expected to be the lightest squarks in supersymmetric theories and the search for these particles is an important experimental task. We therefore present the cross sections for the production processes $p\bar{p}/pp \to \ste\steb$ and $\stz\stzb$ at Tevatron and LHC energies in next-to-leading order supersymmetric QCD. The corrections stabilize the theoretical predictions for the cross sections, and they are positive, thus raising the cross sections to values above the leading-order predictions. Mixed $\ste\stzb/\steb\stz$ pairs can only be generated in higher orders at strongly suppressed rates.

hep-ph↗

arXiv1997

Production of Charged Higgs Boson Pairs in Gluon-Gluon Collisions

The search for charged Higgs bosons, which are predicted in supersymmetric theories, is difficult at hadron colliders if the mass is large. In this paper we present the theoretical set-up for the production of charged Higgs boson pairs at the LHC in gluon-gluon collisions: $pp -> gg -> H^+ H^-$. When established experimentally, the trilinear couplings between charged and neutral CP-even Higgs bosons, $H^+ H^- h^0$ and $H^+ H^- H^0$, can be measured.

hep-ph↗

arXiv1997

Pair production of scalar leptoquarks at the Tevatron

We present the cross section for pair production of scalar leptoquarks $LQ$ in $p\bar{p}$ collisions, $p+\bar{p} \to LQ + \bar{LQ} + X$, at the Fermilab Tevatron in next-to-leading order QCD. Including the higher-order corrections stabilizes the theoretical prediction and increases the size of the cross section for renormalization/factorization scales close to the mass of the leptoquarks. This leads to an increase of the lower bound on the mass of scalar leptoquarks by up to 15 GeV with respect to earlier analyses.

hep-ph↗

arXiv1997

Formation and Decay of Scalar Leptoquarks/Squarks in ep collisions

The cross sections for the formation of scalar resonances, leptoquarks or squarks, in electron/positron-proton collisions at HERA are presented including next-to-leading order QCD corrections. Depending mildly on the mass of the resonances, the K-factors increase the production cross sections by up to 30% if the target quarks are valence quarks. The QCD corrections to the partial decay widths of leptoquarks/squarks to leptons and quarks are small. The electron spectrum in the decays is softened nevertheless by perturbative gluon radiation at a level of 3.4 GeV for a leptoquark/squark mass of 200 GeV.

hep-ph↗