Triphoton production at hadron colliders

We present next-to-leading order predictions for the production of triphoton final states at the LHC and the Tevatron. Our results include the effect of photon fragmentation for the first time and we are able to quantify the impact of different isolation prescriptions. We find that calculations accounting for fragmentation effects at leading order, and those employing a smooth cone isolation where no fragmentation contribution is required, are in reasonable agreement with one another. However, larger differences in the predicted rates arise when higher order corrections to the fragmentation functions are included. In addition we present full analytic results for the $\gamma\gamma\gamma$ and $\gamma\gamma+$jet one-loop amplitudes. These amplitudes, which are particularly compact, may be useful to future higher-order calculations. Our results are available in the Monte Carlo code MCFM.Comment: 16 pages, 4 figure

Trends in the Social [Ir]responsibility of American Multinational Corporations: Increased Power, Diminished Accountability

The purpose of this invited essay is to assess the future of the CSR performance of American multinationals in light of several ongoing trends. These trends include companies’ voluntary CSR programs and the global self-regulatory standards for responsible company activities that are developing in almost every industry. Moreover, the decade-long project at the United Nations to identify multinational companies’ responsibilities with respect to international human rights, ultimately spearheaded by Special Representative John Ruggie, has for the first time established global expectations of responsible corporate activity. At the same time, however, legal developments in the United States may be trending in the opposite direction, toward increased power and diminished accountability for corporations. Two legal developments that highlight this counter-trend will frame this discussion. The first, the Supreme Court’s decision in Citizens United v. Federal Election Commission, 558 U.S. 310 (2010) recognizes a constitutional right for corporations to give financial support to a wide range of electioneering activities, including by using corporate funds to pay for and broadcast advertisements for specific candidates for office. The effect is to allow American companies to further consolidate their already substantial political power. The second, the opinion by the U.S. Court of Appeals for the Second Circuit in Kiobel v. Royal Dutch Petroleum, 621 F.3d 111 (2d Cir. 2010), reh’g en banc denied, 642 F.3d 379 (2011), aff’d, 569 U.S. __ , 133 S. Ct.1659(Apr. 17, 2013), denied the possibility of corporate liability under the Alien Tort Statute for Royal Dutch Shell’s employees’ alleged violations of Nigerian community members’ international human rights. A 2-1 majority held instead that violations of international law could only be asserted against natural persons or nations. The Supreme Court granted certiorari and in a decision handed down on April 17, 2013, the Court unanimously affirmed the judgment of the Second Circuit. The five-Justice opinion of the Court held that the ATS cannot be used to redress violations of the law of nations that occur outside the territory of the United States, except in exceptional circumstances not found in Kiobel. Neither the majority opinion nor the concurrence addressed the corporate liability issue, which means that the Second Circuit’s ruling on that issue remains the law of the Second Circuit — an important outcome, given the significance of the Second Circuit as a venue for ATS cases. Taken together, the overall effect of the Second Circuit’s rejection of corporate liability for human rights violations and the Supreme Court’s rejection of exterritorial application of the ATS to any defendant, corporate or otherwise, is the substantial evisceration of companies’ legal accountability for international human rights violations under the ATS. On a theoretical level, these decisions send mixed messages about corporate personhood and identity. But on a practical level, the two decisions work in unfortunate concert to increase the already considerable political power of U.S. corporations at home, even as they reduce the risk of legal accountability for their actions abroad. By doing so, they shrink the shadow of the law — the threat of hard legal regulation — that has been an important incentive to the adoption of voluntary, soft-law CSR standards. Thus, these legal developments, though ostensibly unrelated to the voluntary pursuit of CSR activity, may in fact act as a disincentive to that activity

The asymptotics of an amplitude for the 4-simplex

An expression for the oscillatory part of an asymptotic formula for the relativistic spin network amplitude for a 4-simplex is given. The amplitude depends on specified areas for each two-dimensional face in the 4-simplex. The asymptotic formula has a contribution from each flat Euclidean metric on the 4-simplex which agrees with the given areas. The oscillatory part of each contribution is determined by the Regge calculus Einstein action for that geometry.Comment: 5 pages amstex, typos correcte

ZγZ\gamma production at NNLO including anomalous couplings

In this paper we present a next-to-next-to-leading order (NNLO) QCD calculation of the processes $pp\rightarrow l^+l^-\gamma$ and $pp\rightarrow \nu\bar\nu\gamma$ that we have implemented in MCFM. Our calculation includes QCD corrections at NNLO both for the Standard Model (SM) and additionally in the presence of $Z\gamma\gamma$ and $ZZ\gamma$ anomalous couplings. We compare our implementation, obtained using the jettiness slicing approach, with a previous SM calculation and find broad agreement. Focusing on the sensitivity of our results to the slicing parameter, we show that using our setup we are able to compute NNLO cross sections with numerical uncertainties of about $0.1\%$, which is small compared to residual scale uncertainties of a few percent. We study potential improvements using two different jettiness definitions and the inclusion of power corrections. At $\sqrt{s}=13$ TeV we present phenomenological results and consider $Z\gamma$ as a background to $H\to Z\gamma$ production. We find that, with typical cuts, the inclusion of NNLO corrections represents a small effect and loosens the extraction of limits on anomalous couplings by about $10\%$.Comment: 30 pages, 14 figure

NLO predictions for a lepton, missing transverse momentum and dijets at the Tevatron

n this letter we investigate the various processes that can contribute to a final state consisting of a lepton, missing transverse momentum and two jets at Next to Leading Order (NLO) at the Tevatron. In particular we consider the production of W/Z + 2 jets, diboson pairs, single top and the tt process with both fully leptonic and semi-leptonic decays. We present distributions for the invariant mass of the dijet system and normalisations of the various processes, accurate to NLO.Comment: 4 pages, 5 figure

Hadronic production of a Higgs boson and two jets at next-to-leading order

We perform an update of the next-to-leading order calculation of the rate for Higgs boson production in association with two jets. Our new calculation incorporates the full analytic result for the one-loop virtual amplitude. This new theoretical information allows us to construct a code including the decay of the Higgs boson without incurring a prohibitive penalty in computer running time. Results are presented for the Tevatron, where implications for the Higgs search are sketched, and also for a range of scenarios at the LHC.Comment: 16 pages, 4 figure

Tullio Regge's legacy: Regge calculus and discrete gravity

The review paper "Discrete Structures in Physics", written in 2000, describes how Regge's discretization of Einstein's theory has been applied in classical relativity and quantum gravity. Here, developments since 2000 are reviewed briefly, with particular emphasis on progress in quantum gravity through spin foam models and group field theories.Comment: 15 pages; a contribution to the forthcoming volume "Tullio Regge: an eclectic genius, from quantum gravity to computer play", Eds. L Castellani, A. Ceresole, R. D'Auria and P. Fr\`e (World Scientific); v2: added references to more relevant work, minor changes to the tex