Colliding Pomerons

We recall the main properties of inclusive particle distributions expected for Pomeron-proton and Pomeron–Pomeron interactions. Due to the small size of the Pomeron we expect larger transverse momenta of secondaries and a smaller probability of multiple interactions, that is a narrower multiplicity distribution. We propose to compare the spectra of secondaries produced in the Pomeron and the proton interactions in terms of the Feynman xF variable. The main difference should be observed for a relatively large xF, that is near the edge of rapidity gaps. Such data offer the opportunity to illuminate the properties of the ‘soft’ or ‘Regge’ Pomeron, which drives the minimum-bias type of events in high energy pp interactions. Besides this, there should be a good opportunity to observe a glueball in the Pomeron fragmentation region

Central exclusive chi (c) meson production at the Tevatron revisited

Motivated by the recent experimental observation of exclusive c events at the Tevatron, we revisit earlier studies of central exclusive scalar c0 meson production, before generalising the existing formalism to include c1 and c2 mesons. Although c0 production was previously assumed to be dominant, we find that the c1 and c2 rates for the experimentally considered c ! J/ ! μ+μ− decay process are in fact comparable to the c0 rate. We have developed a new Monte Carlo event generator, SuperCHIC, which models the central exclusive production of the three c states via this decay chain, and have explored possible ways of distinguishing them, given that their mass differences are not resolvable within the current experimental set-up. Although we find that the severity of current experimental cuts appears to preclude this, the acceptance does not change crucially between the three states and so our conclusions regarding the overall rates remain unchanged. This therefore raises the interesting possibility that exclusive c1 and c2 production has already been observed at the Tevatron

Central Exclusive Production in QCD

We investigate the theoretical description of the central exclusive production process, h1+h2 -> h1+X+h2. Taking Higgs production as an example, we sum logarithmically enhanced corrections appearing in the perturbation series to all orders in the strong coupling. Our results agree with those originally presented by Khoze, Martin and Ryskin except that the scale appearing in the Sudakov factor, mu=0.62 \sqrt{\hat{s}}, should be replaced with mu=\sqrt{\hat{s}}, where \sqrt{\hat{s}} is the invariant mass of the centrally produced system. We confirm this result using a fixed-order calculation and show that the replacement leads to approximately a factor 2 suppression in the cross-section for central system masses in the range 100-500 GeV.Comment: 41 pages, 19 figures; minor typos fixed; version published in JHE

Diffractive Higgs Production by AdS Pomeron Fusion

The double diffractive Higgs production at central rapidity is formulated in terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower, Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple self-consistent holographic framework capable of providing phenomenologically compelling estimates of diffractive cross sections at the LHC. As in the traditional weak coupling approach, we anticipate that several phenomenological parameters must be tested and calibrated through factorization for a self-consistent description of other diffractive process such as total cross sections, deep inelastic scattering and heavy quark production in the central region.Comment: 53 pages, 8 figure

Constraining noncommutative field theories with holography

An important window to quantum gravity phenomena in low energy noncommutative (NC) quantum field theories (QFTs) gets represented by a specific form of UV/IR mixing. Yet another important window to quantum gravity, a holography, manifests itself in effective QFTs as a distinct UV/IR connection. In matching these two principles, a useful relationship connecting the UV cutoff $\Lambda_{\rm UV}$, the IR cutoff $\Lambda_{\rm IR}$ and the scale of noncommutativity $\Lambda_{\rm NC}$, can be obtained. We show that an effective QFT endowed with both principles may not be capable to fit disparate experimental bounds simultaneously, like the muon $g-2$ and the masslessness of the photon. Also, the constraints from the muon $g-2$ preclude any possibility to observe the birefringence of the vacuum coming from objects at cosmological distances. On the other hand, in NC theories without the UV completion, where the perturbative aspect of the theory (obtained by truncating a power series in $\Lambda_{\rm NC}^{-2}$) becomes important, a heuristic estimate of the region where the perturbative expansion is well-defined $E/ \Lambda_{\rm NC} \lesssim 1$, gets affected when holography is applied by providing the energy of the system $E$ a $\Lambda_{\rm NC}$-dependent lower limit. This may affect models which try to infer the scale $\Lambda_{\rm NC}$ by using data from low-energy experiments.Comment: 4 pages, version to be published in JHE

Cross Section Ratios between different CM energies at the LHC: opportunities for precision measurements and BSM sensitivity

The staged increase of the LHC beam energy provides a new class of interesting observables, namely ratios and double ratios of cross sections of various hard processes. The large degree of correlation of theoretical systematics in the cross section calculations at different energies leads to highly precise predictions for such ratios. We present in this letter few examples of such ratios, and discuss their possible implications, both in terms of opportunities for precision measurements and in terms of sensitivity to Beyond the Standard Model dynamics.Comment: 19 pages, 9 figure

Search for electromagnetic properties of the neutrinos at the LHC

Exclusive production of neutrinos via photon-photon fusion provides an excellent opportunity to probe electromagnetic properties of the neutrinos at the LHC. We explore the potential of processes pp-> p gamma gamma p -> p nu anti-nu p and pp -> p gamma gamma p -> p nu anti-nu Z p to probe neutrino-photon and neutrino-two photon couplings. We show that these reactions provide more than seven orders of magnitude improvement in neutrino-two photon couplings compared to LEP limits.Comment: 11 pages, 4 tables, New backgrounds have been adde

Combination of electroweak and QCD corrections to single W production at the Fermilab Tevatron and the CERN LHC

Precision studies of the production of a high-transverse momentum lepton in association with missing energy at hadron colliders require that electroweak and QCD higher-order contributions are simultaneously taken into account in theoretical predictions and data analysis. Here we present a detailed phenomenological study of the impact of electroweak and strong contributions, as well as of their combination, to all the observables relevant for the various facets of the p\smartpap \to {\rm lepton} + X physics programme at hadron colliders, including luminosity monitoring and Parton Distribution Functions constraint, $W$ precision physics and search for new physics signals. We provide a theoretical recipe to carefully combine electroweak and strong corrections, that are mandatory in view of the challenging experimental accuracy already reached at the Fermilab Tevatron and aimed at the CERN LHC, and discuss the uncertainty inherent the combination. We conclude that the theoretical accuracy of our calculation can be conservatively estimated to be about 2% for standard event selections at the Tevatron and the LHC, and about 5% in the very high $W$ transverse mass/lepton transverse momentum tails. We also provide arguments for a more aggressive error estimate (about 1% and 3%, respectively) and conclude that in order to attain a one per cent accuracy: 1) exact mixed ${\cal O}(\alpha \alpha_s)$ corrections should be computed in addition to the already available NNLO QCD contributions and two-loop electroweak Sudakov logarithms; 2) QCD and electroweak corrections should be coherently included into a single event generator.Comment: One reference added. Final version to appear in JHE