L. Cremaldi

Design and performance of the silicon sensors for the CMS barrel pixel detector

The CMS experiment at the LHC includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100X150 um^2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

Catfish: A Monte Carlo simulator for black holes at the LHC

We present a new Fortran Monte Carlo generator to simulate black hole events at CERNs Large Hadron Collider. The generator interfaces to the PYTHIA Monte Carlo fragmentation code. The physics of the BH generator includes, but not limited to, inelasticity effects, exact field emissivities, corrections to semiclassical black hole evaporation and gravitational energy loss at formation. These features are essential to realistically reconstruct the detector response and test different models of black hole formation and decay at the LHC.

Simulation of heavily irradiated silicon pixel sensors and comparison with test beam measurements

Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes free carrier trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a double peak electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

Ionization cooling ring for muons

Practical ionization cooling rings could lead to lower cost or improved performance in neutrino factory or muon collider designs. The ring modeled here uses realistic three-dimensional fields. The performance of the ring compares favorably with the linear cooling channel used in the second U.S. Neutrino Factory Study. The normalized 6D emittance of an ideal ring is decreased by a factor of approximately 240, compared with a factor of only 15 for the linear channel. We also examine such real-world effects as windows on the absorbers and rf cavities and leaving empty lattice cells for injection and extraction. For realistic conditions the ring decreases the normalized 6D emittance by a factor of 49.

Observation, modeling, and temperature dependence of doubly peaked electric fields in irradiated silicon pixel sensors

Abstract We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5 × 10 14 to 5.9 × 10 14 n eq / cm 2 . The model correctly predicts the variation in the profiles as the temperature is changed from - 10 to - 25 ∘ C . The measured charge collection profiles are inconsistent with the linearly varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.

Tests of silicon sensors for the CMS pixel detector

The tracking system of the CMS experiment, currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a silicon pixel detector providing three spacial measurements in its final configuration for tracks produced in high energy pp collisions. In this paper we present the results of test beam measurements performed at CERN on irradiated silicon pixel sensors. Lorentz angle and charge collection efficiency were measured for two sensor designs and at various bias voltages.

Search for CP violation in charged D meson decays

Abstract We report results of a search for CP violation in the singly Cabibbo-suppressed decays D + → K − K + π + , φπ + , K ∗ (892) 0 K + , and π − π + π + based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D + and D − decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters ( A CP ), defined as the difference in the D + and D − decay rates divided by the sum of the decay rates, are measured to be: A CP ( KKπ ) = −0.014±0.029, A CP ( φπ ) = −0.028±0.036, A CP (K ∗ (892)K) = −0.010±0.050 and A CP ( πππ ) = −0.017±0.042.We report results of a search for CP violation in the singly Cabibbosuppressed decays D → KKπ, φπ, K(892)0K+, and πππ based on data from the charm hadroproduction experiment E791 at Fermilab. We search for a difference in the D and D decay rates for each of the final states. No evidence for a difference is seen. The decay rate asymmetry parameters (ACP ), defined as the difference in the D + and D decay rates divided by the sum of the decay rates, are measured to be: ACP (KKπ) = −0.014 ± 0.029, ACP (φπ) = −0.028 ± 0.036, ACP (K(892)K) = −0.010 ± 0.050, and ACP (πππ) = −0.017 ± 0.042. PACS numbers: 11.30.Er, 12.15.Ji, 13.25.Ft, 14.40.Lb Typeset using REVTEX

A Cherenkov Radiation Detector With High Density Aerogels

We have designed a threshold Cherenkov detector at the Rutherford-Appleton Laboratory to identify muons with momenta between 230 and 350 MeV/c. We investigated the properties of three aerogels for the design. The nominal indices of refraction were n = 1.03, 1.07, 1.12, respectively. Two of the samples are of high density aerogel not commonly used for Cherenkov light detection. We present results of an examination of some optical properties of the aerogel samples and present basic test beam results.

Position dependence of charge collection in prototype sensors for the CMS pixel detector

This paper reports on the sensor R&D activity for the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1/spl times/10/sup 15/ n/sub eq//cm/sup 2/ at the CERN PS. Afterward, they were bump bonded to unirradiated readout chips and tested using high energy pions in the H2 beam line of the CERN SPS. The readout chip allows a nonzero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The position dependence of signal is presented and the differences between the two sensor options are discussed.

CMS Hadronic EndCap Calorimeter Upgrade Studies for SLHC “Čerenkov Light Collection From Quartz Plates”

Due to an expected increase in radiation damage under super-LHC conditions, we propose to substitute the scintillator tiles in the original design of the hadronic endcap (HE) calorimeter with quartz plates. Quartz is shown to be radiation hard. Using wavelength shifting fibers, it is possible to collect efficiently the Cerenkov light generated in quartz plates. This paper summarizes the results from various test beams, bench tests, and Geant4 simulations done on methods of collecting light from quartz plates, as well as radiation hardness tests on quartz material.