Strange freezeout

We argue that known systematics of hadron cross sections may cause different particles to freeze out of the fireball produced in heavy-ion collisions at different times. We find that a simple model with two freezeout points is a better description of data than that with a single freezeout, while still remaining predictive. The resulting fits seem to present constraints on the late stage evolution of the fireball, including the tantalizing possibility that the QCD chiral transition influences the yields at sqrt(S)=2700 GeV and the QCD critical point those at sqrt(S)=17.3 GeV

Fermion Dipole Moments in Supersymmetric Models with Explicitly Broken R-parity

We present a simple analysis that allows us to extract the leading mass dependence of the dipole moment of matter fermions that might be induced by new physics. We present explicit results for the supersymmetric model with broken R-parity as an illustration. We show that the extra contributions to the electric dipole moment (edm) of fermions from R-parity violating interactions can occur only at two loop level, contrary to claims in the literature. We further find that unlike the generic lepto-quark models, the extra contributions to the dipole moments of the leptons can only be enhanced by m_b/m_l and not by m_t/m_l relative to the expectations in the Standard Model. An interesting feature about this enhancement of these dipole moments is that it does not involve unknown mixing angles. We then use experimental constraints on the electric dipole moments of electron and neutron to obtain bounds on (the imaginary part of) products of R-parity violating couplings, and show that bounds claimed in the literature are too stringent by many orders of magnitude.Comment: 16 pages latex, 7 figure

γγ\gamma \gamma Processes at High Energy pp Colliders

In this note we investigate the production of charged heavy particles via \gaga\ fusion at high energy pp colliders. We revise previous claims that the \gaga\ cross section is comparable to or larger than that for the corresponding Drell-Yan process at high energies. Indeed we find that the \gaga\ contribution to the total production cross section at pp is far below the Drell-Yan cross section. As far as the individual elastic, semi-elastic and inelastic contributions to the \gaga\ process are concerned we find that they are all of the same order of magnitude.Comment: REVTEX, 12 pages, two uuencoded figures appended at the end of the fil

Single Production of Fourth Family Sneutrino via RPV Couplings at Linear Colliders

The single production of fourth family sneutrino $\tilde{\nu}_{4}$ via R-parity violating interactions in electron-positron collisions has been investigated. We study the decays of $\tilde{\nu}_{4}$ into different flavor dilepton $e^{\pm}\mu^{\mp}$ via R-parity violation. It is shown that R-parity violating couplings $(\lambda_{411},\lambda_{412})$ down to 0.001 will be reachable at future linear colliders which would provide better accuracy comparing to the indirect measurements as complementary to the LHC results.Comment: 11 pages, 6 figure

Stabilizing Hadron Resonance Gas Models against Future Discoveries

We examine the stability of hadron resonance gas models by extending them to take care of undiscovered resonances through the Hagedorn formula. We find that the influence of unknown resonances on thermodynamics is large but bounded. Hadron resonance gases are internally consistent up to a temperature higher than the cross over temperature in QCD; but by examining quark number susceptibilities we find that their region of applicability seems to end even below the QCD cross over. We model the decays of resonances and investigate the ratios of particle yields in heavy-ion collisions. We find that observables such as hydrodynamics and hadron yield ratios change little upon extending the model. As a result, heavy-ion collisions at RHIC and LHC are insensitive to a possible exponential rise in the hadronic density of states, thus increasing the stability of the predictions of hadron resonance gas models

CP Studies of the Higgs Sector

The CP structure of the Higgs sector will be of great interest to future colliders. The measurement of the CP properties of candidate Higgs particles will be essential in order to distinguish models of electroweak symmetry breaking, and to discover or place limits on CP-violation in the Higgs sector. In this report we briefly summarize various methods of determining the CP properties of Higgs bosons at different colliders and identify areas where more study is required. We also provide an example of a synergy between the LHC, an e+e- Linear Collider and a Photon Collider, for the examination of CP-violation in a Two-Higgs-Doublet-Model.Comment: A contribution to the LHC / LC Study Group document; 9 pages, 2 figure

Probing the CP of the Higgs at a γγ\gamma \gamma collider using γγ→ttˉ→lX\gamma \gamma \to t \bar t \to lX

We present results of an investigation to study CP violation in the Higgs sector in $t\bar t$ production at a $\gamma\gamma$-collider. This is done in a model independent way in terms of six form-factors $\{\Re(S_{\gamma}), \Im(S_{\gamma}), \Re(P_{\gamma}), \Im(P_{\gamma}), S_t, P_t\}$ which parameterize the CP mixing in Higgs sector. The angular distribution of the decay lepton from $t/\bar t$ is shown to be independent of any CP violation in the $tbW$ vertex. Hence it can be used as a diagnostic of the CP mixing. We study how well one can probe different combinations of the form factors by measurements of the combined asymmetries that we construct, in the initial state lepton (photon) polarization and the final state lepton charge, using only circularly polarized photons. We show that the method can be sensitive to loop-induced CP violation in the Higgs sector in the MSSM.Comment: Talk presented by A. de Roeck at the International Linear Collider Workshop, Jeju Island, Aug. 26-30,2002, 9 pages, 2 figures, LaTeX, uses A4.st

Determining the CP properties of the Higgs boson

The search and the probe of the fundamental properties of Higgs boson(s) and, in particular, the determination of their charge conjugation and parity (CP) quantum numbers, is one of the main tasks of future high-energy colliders. We demonstrate that the CP properties of a Standard Model-like Higgs particle can be unambiguously assessed by measuring just the total cross section and the top polarization in associated Higgs production with top quark pairs in e+e- collisions.Comment: 4 pages, revtex, uses axodraw (style file included in the submission

Unusual Charged Higgs Signals at LEP-2

We have made a detailed study of the signals produced at LEP-2 from charged scalar bosons whose dominant decay channels are into four fermions. The event rates as well as kinematics of the final states are discussed when such scalars are either pair-produced or are generated through a tree-level interaction involving a charged scalar, the W and the Z. The backgrounds in both cases are discussed. We also suggest the possibility of reconstructing the mass of such a scalar at LEP-2.Comment: 12 pages, LateX, 9 Postscript figures, uses eps