Physics with Like-Sign Muon Beams

We point out that both the specific lepton number content and the high energies potentially attainable with muon-muon colliders make it advisable to consider the technical feasibility of including an option of like-sign incoming beams in the studies towards a proposal to build a muon-muon collider with center-of-mass energies in the TeV region. This capability will add some unique physics capabilities to the project. Special attention will have to be paid to polarization retention for the muons.Comment: 13 pages, uuencoded postscript file, also available from ftp://gluon.hep.physik.uni-muenchen.de/preprints/scipp9534.u

Selective Detectors for High Energy Photons and Electrons

For fast identification of high-energy electrons and photons in heavy backgrounds, a counter was developed consisting of successive layers of lucite and lead. Čerenkov radiation emitted in the lucite slabs is collected onto the photocathode of one 5 inch phototube. The geometry as well as the thickness of inserted lead converters can be adapted to kinematical requirements. At 1 BeV/c incoming momentum, the rejection ratio of e, γ showers vs. π or μ is better than 100:1; i.e., proper discrimination setting will allow rejection of 99% of all π's and μ's, while only 1% of e's and γ's will be lost. Protons make no pulses at all. The response over the face of the counter is uniform. The properties of the counter are checked in detail against the behavior of lead glass Čerenkov counters, and of lead scintillator sandwiches of comparable geometry. Many applications appear to favor this type of counter over others operating on conventional principles

Mesures de vies moyennes par effet Doppler

Des vies moyennes de niveaux nucléaires ont été déterminées par la méthode de l'effet Doppler. Les rayonnements gamma de désexcitation ont été détectés dans des compteurs Ge(Li). Des vies moyennes ont été obtenues pour les niveaux 0,953 MeV de 12B et 6,44 MeV de 14N

Quadratic electroweak corrections for polarized Moller scattering

The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity violating electron-electron scattering asymmetry induced by squaring one-loop diagrams. The calculations are relevant for the ultra-precise 11 GeV MOLLER experiment planned at Jefferson Laboratory and experiments at high-energy future electron colliders. The imaginary parts of the amplitudes are taken into consideration consistently in both the infrared-finite and divergent terms. The size of the obtained partial correction is significant, which indicates a need for a complete study of the two-loop electroweak radiative corrections in order to meet the precision goals of future experiments

The 10th Biennial Hatter Cardiovascular Institute workshop: cellular protection—evaluating new directions in the setting of myocardial infarction, ischaemic stroke, and cardio-oncology

Due to its poor capacity for regeneration, the heart is particularly sensitive to the loss of contractile cardiomyocytes. The onslaught of damage caused by ischaemia and reperfusion, occurring during an acute myocardial infarction and the subsequent reperfusion therapy, can wipe out upwards of a billion cardiomyocytes. A similar program of cell death can cause the irreversible loss of neurons in ischaemic stroke. Similar pathways of lethal cell injury can contribute to other pathologies such as left ventricular dysfunction and heart failure caused by cancer therapy. Consequently, strategies designed to protect the heart from lethal cell injury have the potential to be applicable across all three pathologies. The investigators meeting at the 10th Hatter Cardiovascular Institute workshop examined the parallels between ST-segment elevation myocardial infarction (STEMI), ischaemic stroke, and other pathologies that cause the loss of cardiomyocytes including cancer therapeutic cardiotoxicity. They examined the prospects for protection by remote ischaemic conditioning (RIC) in each scenario, and evaluated impasses and novel opportunities for cellular protection, with the future landscape for RIC in the clinical setting to be determined by the outcome of the large ERIC-PPCI/CONDI2 study. It was agreed that the way forward must include measures to improve experimental methodologies, such that they better reflect the clinical scenario and to judiciously select combinations of therapies targeting specific pathways of cellular death and injury

Theoretical Aspects of Standard-Model Higgs-Boson Physics at a Future e^+ e^- Linear Collider

The Higgs boson is the missing link of the Standard Model of elementary particle physics. We review its decay properties and production mechanisms at a future e^+ e^- linear collider and its e^- e^-, e^+- gamma, and gamma gamma modes, with special emphasis on the influence of quantum corrections. We also discuss how its quantum numbers and couplings can be extracted from the study of appropriate final states.Comment: 23 pages (Latex), 15 figures (Postscript), to appear in Int. J. Mod. Phys.

Photoproduction of \eta mesons on protons in the resonance region:The background problem and the third S_11 resonance

We have constructed an isobar model for the $\eta$-photoproduction on the proton in the energy region up to the photon lab energy $K_0 = 3$ GeV. The data base involved into the fitting procedure includes precise results for the cross section and for the $T$-asymmetry of the process $\gamma p\to\eta p$ near threshold obtained at MAMI and ELSA as well as recent results for the $\Sigma$-asymmetry and for the angular distribution measured at higher energies in Grenoble and also more recent measurements performed at JLab for the photon energies up to 2 GeV. The model includes twelve nucleon resonances: $S_{11}(1535)$, $S_{11}(1650)$, $S_{11}(1825)$, $P_{11}(1440)$,$P_{13}(1720)$, $D_{13}(1520)$, $D_ {15}(1675)$, $F_{15}(1680)$, $F_{17}(1990)$,$G_{17}(2190)$, $G_{19} (2250)$, $H_{19}(2220)$, and the background consisting of the nucleon pole term and the vector meson exchange in the $t$-channel. To explain the observed energy dependence of the integrated cross section, two $s$ -wave resonances, $S_{11}(1650)$ and $S_{11}(1825)$, have to be taken into account along with the dominating $S_{11}(1535)$. The integrated cross section as well as the angular distribution and $\Sigma$ asymmetry predicted by the model are in good agreement with the data. Above the photon energy $K_0 = 2$ GeV, the calculated cross section exhibits an appreciable dependence on the $\rho$- and $\omega$-meson contribution, whose coupling with nucleons is not well defined. Several versions of extending the model to higher energies are considered.Comment: 7 pages, 8 figures, 2 tables, version to appear in Eur.Phys.J.A 22 (2004

Single WRW_R Production in e−e−e^-e^- Collisions at the NLC

Single $W_R$ production in $e^-e^-$ collisions at the NLC can be used to probe the Majorana nature of the heavy neutrinos present in the Left-Right Symmetric Model below the kinematic threshold for their direct production. For colliders in the $\sqrt {s}=1-1.5$ TeV range, typical cross sections of order $1-10 fb$ are obtained, depending on the specific choice of model parameters. Backgrounds arising from Standard Model processes are shown to be small. This analysis greatly extends the kinematic range of previous studies wherein the production of an on-shell, like-sign pair of $W_R$'s at the NLC was considered.Comment: 13pp, 3 figures (available on request), LaTex, SLAC-PUB-647