15216780
Rapidity Gap Higgs Signal at the Tevatron and the LHC
We quantify the rate and the signal-to-background ratio for Higgs --> b anti-b detection in double-diffractive events at the Tevatron and the LHC. The signal is predicted to be very small at the Tevatron, but observable at the LHC. We show that the double-diffractive dijet production may serve as a unique gluon factory. This process can be used also as a Pomeron-Pomeron luminosity monitor.
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.
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
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.
119258384
RG invariants, unification and the role of the messenger scale in General Gauge Mediation
In General Gauge Mediation (GGM) all MSSM soft sfermion masses at a high scale Mmess can be parameterised by three a priori independent scales ΛS; 1,2,3(Mmess). (Similarly the gaugino masses are given by ΛG; 1,2,3(Mmess).) For the first two generations this parameterisation in terms of a set of running ΛS; 1,2,3(μ) — conveniently obtained from appropriate RG invariants — continues to hold all the way down to the electroweak scale. This is not the case for the third generation because of the large Yukawa couplings. Together these two observations imply that the messenger scale is an additional parameter of GGM models.In models where all messengers are in complete GUT multiplets (without significant mass splittings), all ΛS,r are equal at Mmess. Starting from the observable mass spectrum at the electroweak scale we present a strategy to determine if this unification occurs and at which scale. This approach uses data accessible at colliders to gain insight into high scale unification physics beyond the unification of gauge couplings.
14703262
Supersymmetry and the multi-instanton measure
Abstract We propose explicit formulae for the integration measure on the moduli space of charge- n ADHM multi-instantons in N = 1 and N = 2 supersymmetric gauge theories. The form of this measure is fixed by its (super) symmetries as well as the physical requirement of clustering in the limit of large spacetime separation between instantons. We test our proposals against known expressions for n ⩽ 2. Knowledge of the measure for all n allows us to revisit, and strengthen, earlier N = 2 results, chiefly: (1) For any number of flavors N F , we provide a closed formula for F n , the n -instanton contribution to the Seiberg-Witten propotential, as a finite-dimensional collective coordinate integral. This amounts to a solution, in quadratures, of the Seiberg-Witten models, without appeal to electric-magnetic duality. (2) In the conformal case N F = 4, this means reducing to quadratures the previously unknown finite renormalization that relates the microscopic and effective coupling constants, τ micro and τ eff . (3) Similar expressions are given for the 4-derivative/8-fermion term in the gradient expansion of N = 2 supersymmetric QCD.
120078928
Non-perturbative contribution to total cross sections in non-abelian gauge theories
Abstract We consider the instanton-induced contribution to the total cross section of vector boson scattering in the SU (2) gauge theory with and without Higgs mechanism. The exponential suppression of instanton-induced processes disappears asymptotically at energies for above the infrared cutoff for the instanton scale size, which is provided, in the Higgs (confinement) phase, by the vacuum expectation value (virtuality of the gluons). Instanton-induced processes may therefore be important in close-to-mass-shell gluon collisions. Our finding also suggests that electroweak baryon-and lepton-number violation with the associated production of many W-bosons may become important at very high energies.
14693268
Instantons in N=4 Sp(N) and SO(N) theories and the AdS / CFT correspondence
Following work on theories with SU(N) gauge groups, we perform a large-N saddle-point approximation of the measure for ADHM multi-instantons in N=4 supersymmetric gauge theories with symplectic or orthogonal gauge groups. For Sp(N) we find that a saddle-point only exists in the even instanton charge sector. For either Sp(N) or SO(N) the saddle-point solution parametrizes AdS_5 x RP^5, the dual supergravity geometry in the AdS/CFT correspondence for these theories. The instanton measure at large-N has the form of the partition function of ten-dimensional N=1 supersymmetric gauge theory with a unitary gauge group dimensionally reduced to zero dimensions.
62799412
Constraining Dark Sectors at Colliders: Beyond the Effective Theory Approach
We outline and investigate a set of benchmark simplified models with the aim of providing a minimal simple framework for an interpretation of the existing and forthcoming searches of dark matter particles at the LHC. The simplified models we consider provide microscopic QFT descriptions of interactions between the Standard Model partons and the dark sector particles mediated by the four basic types of messenger fields: scalar, pseudoscalar, vector and axial-vector. Our benchmark models are characterized by four to five parameters, including the mediator mass and width, the dark matter mass and the effective coupling(s). In the gluon fusion production channel we resolve the top quark in the loop and compute full top-mass effects for scalar and pseudoscalar messengers. We show the LHC limits and reach at 8 and 14 TeV for models with all four messenger types. We also outline the complementarity of direct detection, indirect detection and LHC bounds for dark matter searches. Finally, we investigate the effects which arise from extending the simplified model to include potential new physics contributions in production. Using the scalar mediator as an example, we study the impact of heavy new physics loops which interfere with the top-mediated loops. Our computations are performed within the mcfm framework, and we provide fully flexible public Monte Carlo implementation.