Stefan Berge

How to pin down the CP quantum numbers of a Higgs boson in its tau decays at the LHC

We investigate how the CP quantum numbers of a neutral Higgs boson or spin-zero resonance, produced at the CERN Large Hadron Collider, can be determined in its tau-pair decay mode. We use a method developed in an earlier paper based on the distributions of two angles and apply it to the major 1-prong tau decays. We show for the resulting dilepton, lepton-pion, and two-pion final states that appropriate selection cuts significantly enhance the discriminating power of these observables. From our analysis we conclude that, provided a Higgs boson will be found at the LHC, it appears feasible to collect the event numbers needed to discriminate between a CP-even and -odd Higgs boson and/or between Higgs boson(s) with CP-conserving and CP-violating couplings after several years of high-luminosity runs.

Transverse momentum resummation at small x for the Tevatron and LHC

Analysis of semi-inclusive DIS hadroproduction suggests broadening of transverse momentum distributions at

Top-Quark Charge Asymmetry with a Jet Handle

x

Transverse momentum resummation at small x for the Tevatron and CERN LHC

below a few

Gluino pair production at linear e + e − colliders

10^{-3}

Gluino pair production in high-energy photon collisions

, which can be modeled in the Collins-Soper-Sterman formalism by a modification of impact-parameter-dependent parton densities. We discuss the consequences of such a modification for the production of electroweak bosons at hadron-hadron colliders. If substantial small-

Transverse momentum resummation at small x for the Fermilab Tevatron and CERN LHC

x

Transverse momentum resummation at smallxfor the Fermilab Tevatron and CERN LHC

broadening is observed in forward Z boson production in the Tevatron Run-2, it will strongly affect predicted transverse momentum distributions for W, Z, and Higgs boson production at the Large Hadron Collider.

Determination of the CP parity of Higgs bosons in their tau decay channels at the ILC

Pairs of top and antitop quarks are produced at the LHC to a large extent in association with a hard jet. We investigate the charge asymmetry in t¯ + j production in quantum chromodynamics (QCD) and with additional massive color-octet vector bosons. The total charge asymmetry at the LHC is suppressed by the large charge-symmetric background from gluon-gluon fusion. We show to what extent the asymmetry can be enhanced by suitable phase space cuts and, in particular, elaborate on the kinematics of the hard jet in the t¯ + j final state. We demonstrate that in QCD, the asymmetry amounts to 1.5% for central jets without an excessive reduction of the cross section. By applying additional kinematical cuts, the asymmetry can be enhanced to 4%, but at the cost of a strong reduction of the cross section. Massive color-octet states can generate sizeable effects in t¯ + j production, both on the charge asymmetry and on the cross section. The charge asymmetry probes both vector and axial-vector couplings to quarks. We show that massive color octets can generate asymmetries up to ±10% for moderate and up to ±30% for strong kinematical cuts to be used in experimental analyses at the LHC. Jet kinematics can be used to obtain further information about the nature of the couplings and thereby to discriminate between different models.

Lepton-mass effects in the decays

Analysis of semi-inclusive DIS hadroproduction suggests broadening of transverse momentum distributions at