The Standard Model: How far can it go and how can we tell?

The Standard Model of particle physics encapsulates our current best understanding of physics at the smallest distances and highest energies. It incorporates Quantum Electrodynamics (the quantised version of Maxwell's electromagnetism) and the weak and strong interactions, and has survived unmodified for decades, save for the inclusion of non-zero neutrino masses after the observation of neutrino oscillations in the late 1990s. It describes a vast array of data over a wide range of energy scales. I review a selection of these successes, including the remarkably successful prediction of a new scalar boson, a qualitatively new kind of object observed in 2012 at the Large Hadron Collider. New calculational techniques and experimental advances challenge the Standard Model across an ever-wider range of phenomena, now extending significantly above the electroweak symmetry breaking scale. I will outline some of the consequences of these new challenges, and briefly discuss what is still to be found.Comment: Write up of a talk given at "Unifying physics and technology in light of Maxwell's equations", a Royal Society meeting organised by A. Zayats, J. Ellis, R. Pike on the 150th anniversary of Maxwell's equation

Highlights of EPS HEP 2019

An opinionated and informal recap of highlights from the EPS HEP 2019 conference in Ghent, including some aspects of flavour physics, neutrinos, high-density QCD, astrophysics and energy frontier collider physics, and some thoughts about the future.Comment: 8 page

Testing the Scalar Triplet Solution to CDF's Fat WW Problem at the LHC

The Type II Seesaw model remains a popular and viable explanation of neutrino masses and mixing angles. By hypothesizing the existence of a scalar that is a triplet under the weak gauge interaction, the model predicts strong correlations among neutrino oscillation parameters, signals at lepton flavor experiments, and collider observables at high energies. We investigate reports that the Type II Seesaw can naturally accommodate recent measurements by the CDF collaboration, which finds the mass of the $W$ boson to be significantly larger than allowed by electroweak precision data, while simultaneously evading constraints from direct searches. Experimental scrutiny of this parameter space in the Type II Seesaw has long been evaded since it is not characterized by ``golden channels'' at colliders but instead by cascade decays, moderate mass splittings, and many soft final states. In this work, we test this parameter space against publicly released measurements made at the Large Hadron Collider. By employing a newly developed tool chain combining MadGraph5\_aMC@NLO and Contur, we find that most of the favored space for this discrepancy is already excluded by measurements of Standard Model final states. We give suggestions for further exploration at Run III of the LHC, which is now underway.Comment: 8 pages (incl. refs.), 3 figures; minor clarifications, matches published versio

Testing the scalar triplet solution to CDF’s heavy W problem at the LHC

The type II seesaw model remains a popular and viable explanation of neutrino masses and mixing angles. By hypothesizing the existence of a scalar that is a triplet under the weak gauge interaction, the model predicts strong correlations among neutrino oscillation parameters, signals at lepton flavor experiments, and collider observables at high energies. We investigate reports that the type II seesaw can naturally accommodate recent measurements by the CDF collaboration, which finds the mass of the W boson to be significantly larger than allowed by electroweak precision data, while simultaneously evading constraints from direct searches. Experimental scrutiny of this parameter space in the type II seesaw has long been evaded since it is not characterized by “golden channels” at colliders but instead by cascade decays, moderate mass splittings, and many soft final states. In this work, we test this parameter space against publicly released measurements made at the Large Hadron Collider. By employing a newly developed tool chain combining MadGraph5_AMC@NLO and CONTUR, we find that most of the favored space for this discrepancy is already excluded by measurements of Standard Model final states. We give suggestions for further exploration at run III of the LHC, which is now under way

Hard underlying event correction to inclusive jet cross sections

Jets observed in hadron-hadron scattering contain a contribution from the underlying event that is produced by spectator interactions taking place incoherently with the major parton-parton collision, due to the extended composite structure of the colliding hadrons. Using a recent measurement of the double parton interaction rate, we calculate that the underlying event may be 2 - 3 times stronger than generally assumed, as a result of semi-hard perturbative multiple-parton interactions. This can have an important influence on the inclusive jet cross section at moderate values of E_T, persisting at the 5 - 10% level to the largest observable E_T. We show how the underlying event can be measured accurately using a generalization of the method first proposed by Marchesini and Webber.Comment: 19 pages, revtex, 8 PostScript figure

North-South divide : contrasting impacts of climate change on crop yields in Scotland and England

Corrigendum published in Journal 2011 8 (54) p.152Effects of climate change on productivity of agricultural crops in relation to diseases that attack them are difficult to predict because they are complex and non-linear. To investigate these crop-disease-climate interactions, UKCIP02 scenarios predicting UK temperature and rainfall under high- and low-CO2 emission scenarios for the 2020s and 2050s were combined with a crop simulation model predicting yield of fungicide-treated winter oilseed rape and with a weather-based regression model predicting severity of phoma stem canker epidemics. The combination of climate scenarios and crop model predicted that climate change will increase yield of fungicide-treated oilseed rape crops in Scotland by up to 0.5 t/ha (15%). By contrast, in southern England the combination of climate scenarios, crop, disease and yield loss models predicted that climate change will increase yield losses from phoma stem canker epidemics to up to 50% (1.5 t/ha) and greatly decrease yield of untreated winter oilseed rape. The size of losses is predicted to be greater for winter oilseed rape cultivars that are susceptible than for those that are resistant to the phoma stem canker pathogen Leptosphaeria maculans. Such predictions illustrate the unexpected, contrasting impacts of aspects of climate change on crop-disease interactions in agricultural systems in different regions.Peer reviewedFinal Accepted Versio

PDF4LHC recommendations for LHC Run II

We provide an updated recommendation for the usage of sets of partondistribution functions (PDFs) and the assessment of PDF and PDF+$\alpha_s$uncertainties suitable for applications at the LHC Run II. We reviewdevelopments since the previous PDF4LHC recommendation, and discuss and comparethe new generation of PDFs, which include substantial information fromexperimental data from the Run I of the LHC. We then propose a new prescriptionfor the combination of a suitable subset of the available PDF sets, which ispresented in terms of a single combined PDF set. We finally discuss tools whichallow for the delivery of this combined set in terms of optimized sets ofHessian eigenvectors or Monte Carlo replicas, and their usage, and provide someexamples of their application to LHC phenomenology

γγ\gamma\gamma Event Generators

The report from the working group on '\gamma\gamma Event Generators' of the LEP 2 workshopComment: 42 pages, tared, gzipped, uuencoded. To be published in the proceedings of the LEP 2 Worksho

Cancer-selective, single agent chemoradiosensitising gold nanoparticles

Two nanometre gold nanoparticles (AuNPs), bearing sugar moieties and/or thiol-polyethylene glycol-amine (PEG-amine), were synthesised and evaluated for their in vitro toxicity and ability to radiosensitise cells with 220 kV and 6 MV X-rays, using four cell lines representing normal and cancerous skin and breast tissues. Acute 3 h exposure of cells to AuNPs, bearing PEG-amine only or a 50:50 ratio of alpha-galactose derivative and PEG-amine resulted in selective uptake and toxicity towards cancer cells at unprecedentedly low nanomolar concentrations. Chemotoxicity was prevented by co-administration of N-acetyl cysteine antioxidant, or partially prevented by the caspase inhibitor Z-VAD-FMK. In addition to their intrinsic cancer-selective chemotoxicity, these AuNPs acted as radiosensitisers in combination with 220 kV or 6 MV X-rays. The ability of AuNPs bearing simple ligands to act as cancer-selective chemoradiosensitisers at low concentrations is a novel discovery that holds great promise in developing low-cost cancer nanotherapeutics