117937632
Electromagnetic pair production
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.
125850380
Multiple Hadron Production in Parton {QCD} Jets
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.
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.
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.
16588286
Recursion relations for gauge theory amplitudes with massive vector bosons and fermions
We apply the on-shell tree-level recursion relations of Britto, Cachazo, Feng and Witten to a variety of processes involving internal and external massive particles with spin. We show how to construct multi-vector boson currents where one or more off-shell vector bosons couples to a quark pair and number of gluons. We give compact results for single vector boson currents with up to six partons and double vector boson currents with up to four partons for all helicity combinations. We also provide expressions for single vector boson currents with a quark pair and an arbitrary number of gluons for some specific helicity configurations. Finally, we show how to generalise the recursion relations to handle massive particles with spin on internal lines using gg→t as an example.
16780904
Breakdown of cluster decomposition in instanton calculations of the gluino condensate
Abstract A longstanding puzzle concerns the calculation of the gluino condensate tr λ 2 16π 2 =cΛ 3 in N =1 supersymmetric SU ( N ) gauge theory: so-called weak-coupling instanton (WCI) calculations give c =1, whereas strong-coupling instanton (SCI) calculations give, instead, c=2 (N−1)!(3N−1) −1/N . By examining correlators of this condensate in arbitrary multi-instanton sectors, we cast serious doubt on the SCI calculation of tr λ 2 16π 2 by showing that an essential step—namely cluster decomposition—is invalid. We also show that the addition of a so-called Kovner-Shifman vacuum (in which tr λ 2 16π 2 =0 ) cannot straightforwardly resolve this mismatch.
8182637
Recursion relations for gauge theory amplitudes with massive particles
We derive general tree-level recursion relations for amplitudes which include massive propagating particles. As an illustration, we apply these recursion relations to scattering amplitudes of gluons coupled to massive scalars. We provide new results for all amplitudes with a pair of scalars and n ≤ 4 gluons. These amplitudes can be used as building blocks in the computation of one-loop 6-gluon amplitudes using unitarity based methods.
16015460
New tests of the pp-wave correspondence
The pp-wave/SYM correspondence is an equivalence relation, H string = ??J , between the hamiltonian H string of string field theory in the pp-wave background and the dilatation operator ? in = 4 Super Yang-Mills in the double scaling limit. We calculate matrix elements of these operators in string field theory and in gauge theory. In the string theory Hilbert space we use the natural string basis, and in the gauge theory we use the basis which is isomorphic to it. States in this basis are specific linear combinations of the original BMN operators, and were constructed previously for the case of two scalar impurities. We extend this construction to incorporate BMN operators with vector and mixed impurities. This enables us to verify from the gauge theory perspective two key properties of the three-string interaction vertex of Spradlin and Volovich: (1) the vanishing of the three-string amplitude for string states with one vector and one scalar impurity; and (2) the relative minus sign in the string amplitude involving states with two vector impurities compared to that with two scalar impurities. This implies a spontaneous breaking of the 2 symmetry of the string field theory in the pp-wave background. Furthermore, we calculate the gauge theory matrix elements of ??J for states with an arbitrary number of scalar impurities. In all cases we find perfect agreement with the corresponding string amplitudes derived from the three-string vertex.
9444196
From branes to branes
Abstract We use the ‘branes within branes’ approach to study the appearance of stable ( p −2)-branes and unstable ( p −1)-branes in type II string theory from p -brane– p -antibrane pairs. Our goal is to describe the emergence of these lower-dimensional branes from brane–antibrane pairs in string theory using a tractable gauge theory language. This is achieved by suspending the original p -brane– p -antibrane pair between two ( p +2)-branes, and describing its dynamics in terms of the worldvolume gauge theory on the spectator ( p +2)-branes. Instantons, monopoles, sphalerons and their higher-dimensional generalizations in this worldvolume gauge theory correspond to stable (BPS) and unstable (non-BPS) branes in string theory. Collisions of stable branes with corresponding antibranes and production of lower-dimensional branes in string theory are described in a straightforward way in gauge theory. Tachyonic modes on the p -brane– p -antibrane worldvolume do not appear in our analysis since we work on the worldvolume of the spectator ( p +2)-branes. Our results on brane descent relations are in agreement with Sen's tachyon condensation approach.