14257235
Multiplicity difference between heavy- and light-quark jets revisited
Abstract.The perturbative QCD approach to multiparticle production predicts a characteristic suppression of particle multiplicity in a heavy-quark jet as compared to a light-quark jet. In the modified leading logarithmic approximation (MLLA) the multiplicity difference $\delta_{Q\ell}$ between heavy- and light-quark jets is derived in terms of a few other experimentally measured quantities. The earlier prediction for b-quarks needs revision in the light of new experimental results and the improvement in the understanding of the experimental data. We now find $\delta_{b\ell} = 4.4\pm0.4$. The updated MLLA results on $\delta_{b\ell}$ and $\delta_{c\ell}$ are compared with the present data from e + e- annihilation. Their expected energy independence is confirmed within the energy range between 29 and 200 GeV; the absolute values are now in better agreement with experiment than in the previous analysis, and the remaining difference can be attributed largely to next-to-MLLA contributions, an important subset of which are identified and evaluated.
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.
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.
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.
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.
16154793
A Brief history of the stringy instanton
The arcane ADHM construction of Yang-Mills instantons can be very naturally understood in the framework of D-brane dynamics in string theory. In this point-of-view, the mysterious auxiliary symmetry of the ADHM construction arises as a gauge symmetry and the instantons are modified at short distances where string effects become important. By decoupling the stringy effects, one can recover all the instanton formalism, including the all-important volume form on the instanton moduli space. We describe applications of the instanton calculus to the AdS/CFT correspondence and higher derivative terms in the D3-brane effective action. In these applications, there is an interesting relation between instanton partition functions, the Euler characteristic of instanton moduli space and modular symmetry. We also describe how it is now possible to do multi-instanton calculations in gauge theory and we resolve an old puzzle involving the gluino condensate in supersymmetric QCD.
14629672
Multi-instanton check of the relation between the prepotential F and the modulus u in N = 2 SUSY Yang-Mills theory
Abstract By examining multi-instantons in N = 2 supersymmetric SU(2) gauge theory, we derive, on very general grounds, and to all orders in the instanton number, a relationship between the prepotential F (Φ), and the coordinate on the quantum moduli space u = 〈TrΦ2〉. This relation was previously obtained by Matone in the context of the explicit Seiberg-Witten low-energy solution of the model. Our findings can be viewed as a multi-instanton check of the proposed exact results in supersymmetric gauge theory.
11515241
Exact results in noncommutative = 2 supersymmetric gauge theories
We study the low-energy dynamics of noncommutative = 2 supersymmetric U(N) Yang-Mills theories in the Coulomb phase. Exact results are derived for the leading terms in the derivative expansion of the wilsonian effective action. We find that in the infrared regime the U(1) subgroup decouples, and the remaining SU(N) is described by the ordinary commutative Seiberg-Witten solution. IR/UV mixing is present in the U(1), but not in SU(N). Our analysis is based on explicit perturbative and multi-instanton calculations.
14801216
Instanton test of non-supersymmetric deformations of the AdS5 × S5
We consider instanton effects in a non-supersymmetric gauge theory obtained by marginal deformations of the = 4 SYM. This gauge theory is expected to be dual to type IIB string theory on the AdS5 times deformed-S5 background. From an instanton calculation in the deformed gauge theory we extract the prediction for the dilaton-axion field τ in dual string theory. In the limit of small deformations where the supergravity regime is valid, our instanton result reproduces the expression for τ of the supergravity solution found by Frolov.
14354109
A two-instanton test of the exact solution of N = 2 supersymmetric QCD
Abstract The exact solution of N = 2 supersymmetric QCD found by Seiberg and Witten includes a prediction for all multi-instanton contributions to the low-energy dynamics. In the case where the matter hypermultiplets are massless, the leading non-perturbative contribution at weak coupling comes from the two-instanton sector. We calculate this contribution from first principles using the exact two-instanton solution of the self-dual Yang-Mills equation found by Atiyah, Drinfeld, Hitchin and Manin. We find exact agreement with the predictions of Seiberg and Witten for all numbers of flavours. We also confirm their predictions for the case of massive hypermultiplets.