We consider a BMN operator with one scalar, φ and one vector, DμZ, impurity field and compute the anomalous dimension both at planar and torus levels. This mixed operator corresponds to a string state with two creation operators which belong to different SO(4) sectors of the background. The anomalous dimension at both levels is found to be the same as the scalar impurity BMN operator. At planar...

Vibrational Feshbach resonances are dominant features of positron annihilation for incident positron energies in the range of the molecular vibrations. Studies in relatively small molecules are described that elucidate the role of intramolecular vibrational energy redistribution into near-resonant multimode states, and the subsequent coupling of these modes to the positron continuum, in suppres...

Enhanced positron annihilation on polyatomic molecules is a long-standing and complex problem. We report the results of calculations of resonant positron annihilation on methyl halides. A free parameter of our theory is the positron binding energy. A comparison with energy-resolved annihilation rates measured for CH3F, CH3Cl, and CH3Br [L. D. Barnes, Phys. Rev. A 74, 012706 (2006)10.1103/PhysRe...

I survey a number of interesting tests of quantum chro-modynamics at the amplitude level which can be carried out in electron-positron annihilation and in photon-photon collisions at low energy. Some of the tests require e + e − center of mass energy as small as √ s = 2 GeV. Other tests which involve a spectrum of energies can be carried out advantageously at high energy facilities using the ra...

Assuming that ρ -mesons exist in a quark-gluon plasma at temperatures close to the QCD phase transition, we calculate the dilepton production rate from q-q̄ annihilation via a ρ -meson state using Vector Meson Dominance. The result is compared to the rates from direct q-q̄ annihilation and from π-π annihilation. Furthermore we discuss the suppression of low mass dileptons if the quarks assume an ...

Indirect dark matter (DM) detection typically involves the observation of standard model (SM) particles emerging from DM annihilation/decay inside regions high concentration. We consider an annihilation scenario in which this reaction has to be initiated by one DMs involved being boosted while other is ambient non-relativistic particle. This "trigger" must created, for example, a previous or de...

The collimation C of a hadronic event in the e + e −-annihilation is defined as the average of cos θ, C =< cos θ >, where θ is the angle of each hadron measured from the thrust axis, and the average is over all the hadrons produced in an event. It is an infrared-stable event-shape parameter. 1−C, the difference between the unity and the average collimation at a given energy, is proportional to ...

We present evidence for a 0 (1450) decaying to KK in pp annihilation at rest in liquid hydrogen in the nal state K L K. This reaction is important for the study of the KK decay mode of scalar resonances, in particular the isovectors a 0 (980) and a 0 (1450). The determination of the a 0 (1450) production also xes the KK coupling of the isoscalar f 0 (1500). We

. We combine the creation and annihilation operators of a scalar field in Minkowski spacetime to obtain the generators of the SU(1,1). We show that the transformation between Minkowski and Rindler vacua can be represented by (pseudo)rotation in the space of the SU(1,1) group. The root of this fact originates from the coordinate transformation between Minkowski and Rindler manifolds that can als...