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. ∗
11354161
The Baryon asymmetry in the Standard Model with a low cut-off
We study the generation of the baryon asymmetry in a variant of the standard model, where the Higgs field is stabilized by a dimension-six interaction. Analyzing the one-loop potential, we find a strong first order electroweak phase transition for Higgs masses up to at least 170 GeV. Dimension-six operators induce also new sources of CP violation. We compute the baryon asymmetry in the WKB approximation. Novel source terms in the transport equations enhance the generated baryon asymmetry. For a wide range of parameters the model predicts a baryon asymmetry close to the observed value.
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.
699497
BARYOGENESIS AT THE ELECTROWEAK PHASE TRANSITION FOR A SUSY MODEL WITH A GAUGE SINGLET
SUSY models with a gauge singlet easily allow for a strongly first order electroweak phase transition (EWPT). We discuss the wall profile, in particular transitional CP violation during the EWPT. We calculate CP violating source terms for the charginos in the WKB approximation and solve the relevant transport equations to obtain the generated baryon asymmetry.
15025301
Electroweak constraints on warped geometry in five dimensions and beyond
Here we consider the tree level corrections to electroweak (EW) observables from standard model (SM) particles propagating in generic warped extra dimensions. The scale of these corrections is found to be dominated by three parameters, the Kaluza-Klein (KK) mass scale, the relative coupling of the KK gauge fields to the Higgs and the relative coupling of the KK gauge fields to fermion zero modes. It is found that 5D spaces that resolve the hierarchy problem through warping typically have large gauge-Higgs coupling. It is also found in D> 5 where the additional dimensions are warped the relative gauge-Higgs coupling scales as a function of the warp factor. If the warp factor of the additional spaces is contracting towards the IR brane, both the relative gauge-Higgs coupling and resulting EW corrections will be large. Conversely EW constraints could be reduced by finding a space where the additional dimension’s warp factor is increasing towards the IR brane. We demonstrate that the Klebanov Strassler solution belongs to the former of these possibilities.
8301145
Higgs mechanism and bulk gauge boson masses in the Randall-Sundrum model
Assuming the breaking of gauge symmetries by the Higgs mechanism, we consider the associated bulk gauge boson masses in the Randall-Sundrum background. With the Higgs field confined on the TeV-brane, the W and Z boson masses are naturally an order of magnitude smaller than their Kaluza-Klein excitation masses. The electroweak precision data require the lowest excited state to lie above about 30 TeV, with fermions on the TeV-brane. This bound is reduced to about 10 TeV if the fermions reside sufficiently close to the Planck-brane. Thus, some tuning of parameters is needed. We also discuss the bulk Higgs case, where the bounds are an order of magnitude smaller.
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.
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.
8636737
The universal sampling ADC readout system of the COMPASS experiment
The COMPASS experiment (COmpact Muon Proton Apparatus for Structure and Spectroscopy) is a fixed target experiment located at the CERN Super Proton Synchrotron. The physics program is focused on the study of hadron structure and hadron spectroscopy with high intensity muon and hadron beams, up to 160 GeV/c for muons and 190 GeV/c for hadrons respectively. To allow the tracking of charged particles with very low and as well very high momentum, COMPASS comprises two magnetic spectrometer stages extending to a total length of 60 m. From the data acquisition point of view, about 200000 analog detector channels have to be read along the complete experiment. Depending on the detector signal characteristics and the number of channels, this task is realized by frontend electronics using either dedicated ASICs and/or sampling analog-to-digital (ADC) or time-to-digital (TDC) components. The sampling ADC based readout system of the COMPASS experiment comprises today over 127k channels equipped with the APV25 frontend ASIC and 5728 direct sampling channels. An important feature from the beginning was the combination of data transfer, clock and trigger distribution and configuration access within a standardized serial interface between the different ADC modules and the first stage of data concentrator modules. By choosing between a copper or fiber realization for this interface, either a low cost interconnect or a link with galvanic decoupling can be realized. The ongoing development of the sampling ADC electronics is focused on the migration toward the Advanced Telecom Computing Architecture (ATCA) crate standard, to overcome the backplane bandwidth limitations in VME systems. In addition, the ATCA standard provides better cooling and monitoring capabilities. To simplify the transition to ATCA, the MSADC module was already realized as a mezzanine card, which can be mounted on an ATCA based carrier card as well. In addition, the MSADC card fits also to the MicroTCA form factor, which allows to provide a handy building block for laboratory based data acquisition systems.
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.
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.