119266543
Proton opacity in the light of LHC diffractive data
We show that collider data on elastic pp (and $p\bar{p}$) scattering, including the LHC TOTEM data at 7 TeV, can be well described by a 3-channel eikonal model with only one Pomeron, with parameters that are naturally linked to the perturbative QCD (BFKL) framework. The proton opacity, determined in this way, is then used to account for sizeable absorptive effects. We study the recent measurements of dσ/dΔη made by the ATLAS collaboration, where they select events with large rapidity gaps Δη. We demonstrate that the absorptive corrections noticeably change both the value and the Δη dependence of the cross section. We find that our parameter-free calculation is in agreement with these ATLAS data.
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.
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.
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.
116099235
What is interesting about the region of small momentum transfers at high energies
16221672
How suppressed are the radiative interference effects in heavy unstable particle production
Abstract We present a “theorem” which quantifies, for inclusive processes, the level of suppression of the radiative interference effects between the production and decay stages of heavy unstable particles. The theorem, which is based on very general physical arguments, is applicable to all orders in the coupling.
53142727
Higgs vacuum stability from the dark matter portal
A bstractWe consider classically scale-invariant extensions of the Standard Model (CSI ESM ) which stabilise the Higgs potential and have good dark matter candidates. In this framework all mass scales, including electroweak and dark matter masses, are generated dynamically and have a common origin. We consider Abelian and non-Abelian hidden sectors portally coupled to the SM with and without a real singlet scalar. We perform a careful analysis of RG running to determine regions in the parameter space where the SM Higgs vacuum is stabilised. After combining this with the LHC Higgs constraints, in models without a singlet, none of the regained parameter space in Abelian ESMs, and only a small section in the non-Abelian ESM survives. However, in all singlet-extended models we find that the Higgs vacuum can be stabilised in all of the parameter space consistent with the LHC constraints. These models naturally contain two dark matter candidates: the real singlet and the dark gauge boson in non-Abelian models. We determine the viable range of parameters in the CSI ESM framework by computing the relic abundance, imposing direct detection constraints and combining with the LHC Higgs constraints. In addition to being instrumental in Higgs stabilisation, we find that the singlet component is required to explain the observed dark matter density.
118711313
Multiparticle Higgs and vector boson amplitudes at threshold
A bstractIn a spontaneously broken gauge theory we consider (sub)-processes in which one virtual intermediate state (it can be a Higgs or a gauge field) produces many on-shell Higgses and massive vector bosons. In the kinematic regime where all final states are produced on their mass threshold, we show how to compute iteratively all tree-level amplitudes A1→n+m$$ {\mathcal{A}}_{1\to n+ m} $$ involving an arbitrary number n of Higgs bosons and m of longitudinal vector bosons in the final state, and list the amplitudes coefficients for up to n=32 and m=32. Wefindthattheseamplitudesexhibitfactorialgrowthnotonlyinthenumberof scalar fields, but also in the number of longitudinal gauge fields, A1→n+m$$ {\mathcal{A}}_{1\to n+ m} $$ ~ n! m!. This growth is not expected to disappear at loop-level in the fixed-order perturbation theory. We conclude that at energies accessible at the next generation of hadron colliders, such as the 50-100 TeV FCC, where s^$$ \sqrt{\widehat{s}} $$ is sufficient to produce ≫1/αW of W, Z and H, perturbation theory breaks down when applied to the multiparticle electroweak production, at least near the kinematic multiparticle mass threshold where the electroweak gauge-Higgs sector becomes strongly coupled.
118108888
The valley method and its applications to the instanton-induced phenomena in non-Abelian gauge theories
119202861
Emergence of the electroweak scale through the Higgs portal
A bstractHaving discovered a candidate for the final piece of the Standard Model, the Higgs boson, the question remains why its vacuum expectation value and its mass are so much smaller than the Planck scale (or any other high scale of new physics). One elegant solution was provided by Coleman and Weinberg, where all mass scales are generated from dimensionless coupling constants via dimensional transmutation. However, the original Coleman-Weinberg scenario predicts a Higgs mass which is too light; it is parametrically suppressed compared to the mass of the vectors bosons, and hence is much lighter than the observed value. In this paper we argue that a mass scale, generated via the Coleman-Weinberg mechanism in a hidden sector and then transmitted to the Standard Model through a Higgs portal, can naturally explain the smallness of the electroweak scale compared to the UV cutoff scale, and at the same time be consistent with the observed value. We analyse the phenomenology of such a model in the context of present and future colliders and low energy measurements.
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.