73540275
Numerical approach to multi-dimensional phase transitions
We present an algorithm for numerically analysing the bounce solution for first-order phase transitions. Our approach is well suited to treating phase transitions with several fields. The algorithm consists of two parts. In the first part the bounce solution without damping is determined; in this case energy is conserved. In the second part the continuation to the physically relevant case with damping is performed. The approach presented is numerically stable and easily implemented.
16265499
Bubble wall velocity in the minimal supersymmetric light stop scenario
We build on existing calculations of the wall velocity of the expanding bubbles of the broken symmetry phase in a first-order electroweak phase transition within the light stop scenario (LSS) of the MSSM. We carry out the analysis using the 2-loop thermal potential for values of the Higgs mass consistent with present experimental bounds. Our approach relies on describing the interaction between the bubble and the hot plasma by a single friction parameter, which we fix by matching to an existing 1-loop computation and extrapolate to our regime of interest. For a sufficiently strong phase transition (in which washout of the newly created baryon asymmetry is prevented) we obtain values of the wall velocity, vw≈0.05, far below the speed of sound in the medium, and not very much deviating from the previous 1-loop calculation. We find that the phase transition is about 10% stronger than suggested by simply evaluating the thermal potential at the critical temperature. We also comment on the relevance of our results to extended models, such as the NMSSM.
123226903
Neutrino oscillations and warped geometry.
It is shown how small Dirac and Majorana masses for neutrinos arise in five dimensional models with warped geometry. The atmospheric and solar neutrino anomalies can be satisfactorily resolved. Rare processes, such as proton decay, neutrinoless double beta decay and flavor violation, may provide valuable information on the higher dimensional theory.
121566694
Neutrino oscillations, rare decays and warped geometry
We discuss how the solar and atmospheric neutrino anomalies can be satisfactorily resolved via neutrino oscillations in a five-dimensional framework with warped geometry. In one particularly significant example, no new fields such as singlet (right-handed) neutrinos have to be introduced. We also consider rare processes including proton and neutrinoless double beta decays. The Kaluza–Klein excitations of the standard model particles are predicted to possess masses in the 10 TeV range.
16805200
Flavor violation and warped geometry
Extra dimensions have interesting consequences for flavor physics. We consider a setup where the standard model fermions and gauge fields reside in the bulk of a warped extra dimension. Fermion masses and mixings are explained by flavor dependent fermion locations, without relying on hierarchical Yukawa couplings. We discuss various flavor violating processes induced by (Kaluza–Klein) gauge boson exchange and non-renormalizable operators. Experimental constraints are satisfied with a Kaluza–Klein scale of about 10 TeV. Some processes, such as muon–electron conversion, are within reach of next generation experiments.
16466682
The supersymmetric standard model
This set of lectures introduces at an elementary level the supersymmetric Standard Model and discusses some of its phenomenological properties. ∗
111119743
Upgrade of the COMPASS calorimetric trigger
In 2009 COMPASS performed a short measurement of neutral Primakoff reactions, characterised by highly energetic photons in one of the two electromagnetic calorimeters. A digital trigger was implemented in the existing readout electronics which calculates the energy released in the central region of the calorimeter. In 2012 a long measurement of these processes has been performed. In order to extend the kinematic range to lower energetic photons the trigger system has been upgraded in a way to be more selective to specific physics channels. The new ADC firmware preserves hit information and provides it to newly developed backplane trigger modules. There hits from all three thousand channels are processed and the trigger decision is made.
47544178
A digital trigger for the electromagnetic calorimeter at the COMPASS experiment
At the COMPASS experiment at CERN's SPS many physics channels containing neutral particles are studied. These particles are identified by two electromagnetic calorimeters covering different transfers regions. For certain physics the main signature is described by these neutral particles which requires a calorimetric trigger system. The method described here is fully based on the existing front end electronics and uses digital pulse shape analysis techniques. This approach allows to implement a flexible trigger system as well as to reduce cost by avoiding to produce new electronic components. The implementation of this new trigger as well as the performance measured during the 2009 run will be discussed.
14827287
FPGA based data acquisition system for COMPASS experiment
This paper presents the current data acquisition system (DAQ) of the COMPASS experiment at CERN and discusses development of a new DAQ. The aim of the new DAQ is to substitute software event building by structure composed of special FPGA cards that will do the event building. The software part of the new DAQ is robust multinode system with high emphasis on reliability. It is based on state machines and implemented in C++ with usage of the QT framework, the DIM library, and the IPBus technology. A prototype of the system has been developed and tested. The new DAQ software fulfills given requirements.
118063177
Measurement of the Pion Polarizability at COMPASS
The value of the pion polarizability is predicted with high precision by Chiral Perturbation Theory. However, the existing experimental values are at tension with this prediction as well as among themselves. The COMPASS experiment at the CERN SPS accesses pion-photon reactions via the Primakoff effect, where high-energetic pions react with the quasi-real photon field surrounding the target nuclei. Flagship channel is the Primakoff reaction in which a single real photon is produced, giving access to pion Compton scattering. Using this process the pion polarizability is extracted from the measured cross-section shape. End of 2009 COMPASS performed a measurement of the pion polarizability using a nickel target. The large amount of data collected in combination with the possibility to study systematic effects using the analogous reaction with a muon beam, the most precise experimental value to date was determined.
113403181
New data acquisition system for the COMPASS experiment
The modern market offers low cost high performance FPGA integrated circuits equipped with dozens of multi gigabit serial links making them ideal devices for data transmission and data sorting applications. Therefore we have designed the new DAQ system that would perform the detector readout and event building in a custom made FPGA based hardware. The software part will provide the control and monitoring function. Currently, the prototypes of the new FPGA card are being tested and the control and monitoring software is being prepared for the tests with the real hardware.