118257227
Angular distribution of photon bremsstrahlung at collision of ultrarelativistic electrons
124029542
On the sensitivity of the inclusive distributions in parton jets to the coherence effects in QCD gluon cascades
The KNO multiplicity distributions and properties of two-particle correlations in QCD jets are considered in the framework of the perturbative approach accounting for effects of the coherence in the soft gluon bremsstrahlung.
117871006
Pomeron universality from identical pion correlations at the LHC
Abstract Bose–Einstein correlations of identical pions produced in high-energy pp collisions at the LHC allow a probe of the Pomeron exchange mechanism. The size of the domain which emits the pions depends on the multiplicity of events, but not on the collider energy. This confirms the universal structure of Pomeron exchange. The data at relatively low multiplicities indicate that the size of the source created by one-Pomeron exchange is much less than the size of the proton.
119379184
Radiative corrections to the hadronic cross-section measurement at DA$\Phi$NE
Abstract. The hadronic invariant mass distribution for the process of electron–positron annihilation into a pair of charged pions accompanied by a photon radiated from the initial state has been studied for the region of DA$\Phi$NE energies. The Born cross–section and the electromagnetic radiative corrections to it are calculated for realistic conditions of the KLOE detector. The dependence on the physical parameters which define the event selection is obtained.
125850380
Multiple Hadron Production in Parton {QCD} Jets
119436494
QCD Interconnection Effects
Heavy objects like the W, Z and t are short-lived compared with typical hadronization times. When pairs of such particles are produced, the subsequent hadronic decay systems may therefore become interconnected. We study such potential effects at Linear Collider energies.
14098895
Gluino condensate and magnetic monopoles in supersymmetric gluodynamics
We examine supersymmetric SU(N) gauge theories on R3 × S1 with a circle of circumference β. These theories interpolate between four-dimensional N = 1 pure gauge theory for β = ∞ and three-dimensional N = 2 gauge theory for β = 0. The dominant field configurations of the R3 × S1 SU(N) theories in the semi-classical regime arise from N varieties of monopole. Periodic instanton configurations correspond to mixed configurations of N single monopoles of the N different types. We semi-classically evaluate the non-perturbatively generated superpotential of the R3 × S1 theory and hence determine its vacuum structure. to the gluino condensate in these theories and take the decompactification limit β = ∞. In this way we obtain a value for the gluino condensate in the four-dimensional N = 1 supersymmetric SU(N) Yang-Mills theory, which agrees with the previously known ‘weak coupling’ expression but not with the ‘strong coupling’ expression derived in the early literature solely from instanton considerations. Moreover, we discover that the superpotential gives a mass to the dual (magnetic) photon, which implies confinement of the original electric photon and disappearance of all the massless modes.
120263136
Higher twist effects in the Drell‐Yan process
We calculate the angular distribution of the lepton produced in the Drell‐Yan reaction taking into account pion bound state effects. We work in the kinematic region where one of the pion constituents goes far off shell, which allows us to treat the bound state problem pertubatively. We show that the angular distribution is very sensitive to the shape of the pion distribution amplitude. The model we discuss fits the data if we choose a two‐humped pion distribution amplitude suggested by QCD sum rules.
2910926
MULTI-INSTANTONS, THREE-DIMENSIONAL GAUGE THEORY, AND THE GAUSS-BONNET-CHERN THEOREM
Abstract We calculate multi-instanton effects in a three-dimensional gauge theory with N = 8 supersymmetry and gauge group SU (2). The k -instanton contribution to an eight-fermion correlator is found to be proportional to the Gauss-Bonnet-Chem integral of the Gaussian curvature over the centered moduli space of charge- k BPS monopoles, M k . For k = 2 the integral can be evaluated using the explicit metric on M 2 found by Atiyah and Hitchin. In this case the integral is equal to the Euler character of the manifold. More generally the integral is the volume contribution to the index of the Euler operator on M k which may differ from the Euler character by a boundary term. We conjecture that the boundary terms vanish and evaluate the multi-instanton contributions using recent results for the cohomology of M k We comment briefly on the implications of our result for a recently proposed test of M(atrix) theory.
6234472
Fermion number violation in the background of a gauge field in Minkowski space
Abstract Anomalous fermion number violation is studied in the background of a pure SU(2) gauge field in Minkowski space using the method of N. Christ. It is demonstrated that the chiral fermion number is violated by at most an integer amount. Then the method is applied for a spherically symmetric Minkowski space classical gauge field in the background. These classical gauge fields are finite energy solutions to pure SU(2) equations of motion with in general non-integer topological charge. We show that in the classical background which during a finite time-interval matches such solutions the fermion number violation is integer and non-zero. In particular, we calculate the violation of the fermiion number in the presence of Luscher-Schechter solutions. The meaning of the anomaly equation and applications to QCD and electroweak theory are briefly discussed. We also comment on the relation of the results of this paper to the previous work.
119112809
Leptogenesis and neutrino oscillations in the classically conformal standard model with the Higgs portal
A bstractThe Standard Model with an added Higgs portal interaction and no explicit mass terms is a classically scale-invariant theory. In this case the scale of electroweak symmetry breaking can be induced radiatively by the Coleman-Weinberg mechanism operational in a hidden sector, and then transmitted to the Standard Model through the Higgs portal. The smallness of the generated values for the Higgs vev and mass, compared to the UV cutoff of our classically scale-invariant effective theory, is naturally explained by this mechanism.We show how these classically conformal models can generate the baryon asymmetry of the Universe without the need of introducing mass scales by hand or their resonant fine-tuning. The minimal model we consider is the Standard Model coupled to the Coleman-Weinberg scalar field charged under the U(1)B−L gauge group. Anomaly cancellation requires automatic inclusion of three generations of right-handed neutrinos. Their GeV-scale Majorana masses are induced by the Coleman-Weinberg field and lead to the generation of active neutrino masses through the standard see-saw mechanism. Leptogenesis occurs via flavour oscillations of right-handed sterile neutrinos and is converted to the baryon asymmetry by electroweak sphalerons.