18231969
One-loop Higgs plus four gluon amplitudes: full analytic results
We consider one-loop amplitudes of a Higgs boson coupled to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of a complex field ϕ that couples to the self-dual field strengths and compute the one-loop corrections to the ϕ-NMHV amplitude, which contains one gluon of positive helicity whilst the remaining three have negative helicity. We use four-dimensional unitarity to construct the cut-containing contributions and a hybrid of Feynman diagram and recursive based techniques to determine the rational piece. Knowledge of the ϕ-NMHV contribution completes the analytic calculation of the Higgs plus four gluon amplitude. For completeness we also include expressions for the remaining helicity configurations which have been calculated elsewhere. These amplitudes are relevant for Higgs plus jet production via gluon fusion in the limit where the top quark is large compared to all other scales in the problem.
118200237
Higgs + 2 jets: Compact Analytic Results
This report describes the recent efforts to compute analytic formulae for the Next-to-Leading-Order (NLO) QCD corrections to Higgs plus two jet production at hadron colliders. In these calculations the Higgs boson couples to gluons via a top-quark loop which is integrated out to form an effective vertex. The amplitudes are further simplified by splitting the real Higgs scalar into the sum of two complex scalars phi and phi^dagger. Four-dimensional unitarity is used to construct the cut-containing pieces of the amplitude, while a variety of bootstrap and Feynman diagram techniques are used to construct the rational pieces. The results described here are valid in the limit of a large top quark mass and when the transverse momenta of the jets are less than mt.
73541374
The matrix element method at next-to-leading order
A bstractThis paper presents an extension of the matrix element method to next-to-leading order in perturbation theory, for electro-weak final states. To accomplish this we have developed a method to calculate next-to-leading order weights on an event-by-event basis. This allows for the definition of next-to-leading order likelihoods in exactly the same fashion as at leading order, thus extending the matrix element method to next-to-leading order. A welcome by-product of the method is the straightforward and efficient generation of unweighted next-to-leading order events. As examples of the application of our next-to-leading order matrix element method we consider the measurement of the mass of the Z boson and also the search for the Higgs boson in the four lepton channel.
118842322
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.
349168
One-loop ϕ-MHV amplitudes using the unitarity bootstrap: the general helicity case
We consider a Higgs boson coupled to gluons via the five-dimensional effective operator HtrGμνGμν. We treat H as the real part of a complex field that couples to the selfdual gluon field strengths and compute the one-loop corrections to the -MHV amplitudes involving , two negative helicity gluons and an arbitrary number of positive helicity gluons. Our results generalise earlier work where the two negative helicity gluons were constrained to be colour adjacent. We use four-dimensional unitarity to construct the cut-containing contributions and the recently developed recursion relations to obtain the rational contribution for an arbitrary number of external gluons. We solve the recursion relations and give explicit results for up to four external gluons. These amplitudes are relevant for Higgs plus jet production via gluon fusion in the limit where the top quark mass is large compared to all other scales in the problem.
117588033
Extending the Matrix Element Method to Next-to-Leading Order
We discuss the extension of the matrix element method (MEM) to Next-to-Leading Order (NLO) in perturbation theory. In particular we focus on the production of a Standard Model Higgs boson which decays into four leptons.
119118160
A Search for Microwave Emission From Ultra-High Energy Cosmic Rays
We present a search for microwave emission from air showers induced by ultrahigh energy cosmic rays with the microwave detection of air showers experiment. No events were found, ruling out a wide range of power flux and coherence of the putative emission, including those suggested by recent laboratory measurements.
23746592
Front-end electronics and data acquisition system for the MIDAS experiment
The MIDAS (MIcrowave Detection of Air Showers) experiment, a prototype detector to characterize the microwave emission of air showers induced by high energy cosmic rays, has been recently commissioned at the University of Chicago. The receivers, 53 feed horns in the 4GHz band, send the signal to fast power detectors which have logarithmic response to the input RF power. The integrated output signal is continuously digitized in custom 14-bit 20 MHz ADC modules. Data are then processed locally with on-board Field Programmable Gate Arrays (FPGAs) where the trigger logic allows discrimination of events. Local trigger pulses are sent out to a Master Board where a system-wise trigger pulse is generated and sent back to the ADC Modules. After each trigger, a 100 us time stream of data is packed and buffered for readout via the VME back plane. A VME GPS module is also used for precise timing information. Design, specifications of the electronic components, a description of the implemented trigger logic, and preliminary test results will be presented in this contribution.
118789728
The MIDAS experiment: A prototype for the microwave emission of Ultra-High Energy Cosmic Rays
Recent measurements suggest that extensive air showers initiated by ultra-high energy cosmic rays (UHECR) emit signals in the microwave band of the electromagnetic spectrum caused by the collisions of the free-electrons with the atmospheric neutral molecules in the plasma produced by the passage of the shower. Such emission is isotropic and could allow the detection of air showers with 100% duty cycle and a calorimetric-like energy measurement, a significant improvement over current detection techniques. We have built MIDAS (MIcrowave Detection of Air Showers), a prototype of microwave detector, which consists of a 4.5 m diameter antenna with a cluster of 53 feed-horns in the 4 GHz range. The details of the prototype and first results will be presented.