Particle theory

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Neutrino-Flavoured Sneutrino Dark Matter

(2009)

Authors:

John March-Russell, Christopher McCabe, Matthew McCullough

A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project

(2009)

Authors:

Tancredi Carli, Dan Clements, Amanda Cooper-Sarkar, Claire Gwenlan, Gavin P Salam, Frank Siegert, Pavel Starovoitov, Mark Sutton

On Gauge Threshold Corrections for Local IIB/F-theory GUTs

(2009)

Authors:

JP Conlon, E Palti

Abstract:

We study gauge threshold corrections for local GUT models in IIB/F-theory. Consistency with holomorphy requirements of supergravity and the Kaplunovsky-Louis formula implies that the unification scale is enhanced by the bulk radius R from the string scale to M_X =RM_S. We argue that the stringy interpretation of this is via a locally uncancelled tadpole sourced by the hypercharge flux. This sources closed string modes propagating into the bulk; equivalently open string gauge coupling running up to the winding scale M_X. The enhancement to R M_s is tied to GUT breaking by a globally trivial hypercharge flux and will occur in all models realising this mechanism.

Exploring Positive Monad Bundles And A New Heterotic Standard Model

(2009)

Authors:

Lara B Anderson, James Gray, Yang-Hui He, Andre Lukas

Freeze-In Production of FIMP Dark Matter

ArXiv 0911.1120 (2009)

Authors:

Lawrence J Hall, Karsten Jedamzik, John March-Russell, Stephen M West

Abstract:

We propose an alternate, calculable mechanism of dark matter genesis, "thermal freeze-in," involving a Feebly Interacting Massive Particle (FIMP) interacting so feebly with the thermal bath that it never attains thermal equilibrium. As with the conventional "thermal freeze-out" production mechanism, the relic abundance reflects a combination of initial thermal distributions together with particle masses and couplings that can be measured in the laboratory or astrophysically. The freeze-in yield is IR dominated by low temperatures near the FIMP mass and is independent of unknown UV physics, such as the reheat temperature after inflation. Moduli and modulinos of string theory compactifications that receive mass from weak-scale supersymmetry breaking provide implementations of the freeze-in mechanism, as do models that employ Dirac neutrino masses or GUT-scale-suppressed interactions. Experimental signals of freeze-in and FIMPs can be spectacular, including the production of new metastable coloured or charged particles at the LHC as well as the alteration of big bang nucleosynthesis.