Time Resolution of a Few Nanoseconds in Silicon Strip Detectors Using the APV25 Chip

The APV25 front-end chip for the CMS Silicon Tracker has a peaking time of 50 ns, but confines the signal to a single clock period (=bunch crossing) with its internal “deconvolution” filter. This method requires a beam-synchronous clock and thus cannot be applied to a (quasi-) continuous beam. Nevertheless, using the multi-peak mode of the APV25, where 3 (or 6,9,12,...) consecutive shaper output samples are read out, the peak time can be reconstructed externally with high precision. Thus, offtime hits can be discarded which results in significant occupancy reduction. We will describe this method, results from beam tests and the intended implementation in an upgrade of the BELLE Silicon Vertex Detector

Construction and Performance of a Double-Sided Silicon Detector Module Using the Origami Concept

The APV25 front-end chip with short shaping time will be used in the Belle II Silicon Vertex Detector (SVD) in order to achive low occupancy. Since fast amplifiers are more susceptible to noise caused by their capacitive input load, they have to be placed as close to the sensor as possible. On the other hand, material budget inside the active volume has to be kept low in order to constrain multiple scattering. We built a low mass sensor module with double-sided readout, where thinned APV25 chips are placed on a single flexible circuit glued onto one side of the sensor. The interconnection to the other side is done by Kapton fanouts, which are wrapped around the edge of the sensor, hence the name Origami. Since all front-end chips are aligned in a row on the top side of the module, cooling can be done by a single aluminum pipe. The performance of the Origami module was evaluated in a beam test at CERN in August 2009, of which first results are presented here

Readout and Data Processing Electronics for the Belle-II Silicon Vertex Detector

A prototype readout system has been developed for the future Belle-II Silicon Vertex Detector at the Super-KEK-B factory in Tsukuba, Japan. It will receive raw data from double-sided sensors with a total of approximately 240,000 strips read out by APV25 chips at a trigger rate of up to 30kHz and perform strip reordering, pedestal subtraction, a two-pass common mode correction and zero suppression in FPGA firmware. Moreover, the APV25 will be operated in multi-peak mode, where (typically) six samples along the shaped waveform are used for precise hit-time reconstruction which will also be implemented in FPGAs using look-up tables

The CMS Pixel FED

The innermost detector of the CMS Experiment consists of 66 million silicon pixels. The hit data has to be read out and must be digitized, synchronized, formatted and transferred over the S-Link to the CMS DAQ. The amount of data can only be handled because the readout chip (ROC) delivers zero-suppressed data above an adjustable threshold for every pixel. The Pixel FED 9U VME module receives an analog optical signal, which is subsequently digitized and processed. The position of the pixel on a module is transmitted with five symbols coded in six pulse height steps each. The data of 36 inputs build a final event data block. The data block from each detector module with either 16 or 24 ROCs differs in length and arrival time. Depending on the data length and trigger rate, there can be a skew of several events between any two inputs. That is possible because the ROC has a multievent time stamp memory and the readout bandwith is limited. Finally the information processed by the Pixel FED will be transferred over the S-Link to the CMS DAQ. Each module must be able to process a trigger rate of 100 kHz or, if in trouble, to send an alarm signal. The number of inputs is limited by the maximum data transmission rate of the S-Link (640 MB/s) for the expected high luminosity of LHC. The data flow on the module is continuously controlled. Errors are written in an error memory, included in the data stream and if critical sent to the general CMS readout control

Calibration of dosemeters used in mammography with different X ray qualities: Euromet Project No. 526

The effect of different X ray radiation qualities on the calibration of mammographic dosemeters was investigated within the framework of a EUROMET (European Collaboration in Measurement Standards) project. The calibration coefficients for two ionization chambers and two semiconductor detectors were established in 13 dosimetry calibration laboratories for radiation qualities used in mammography. They were compared with coefficients for other radiation qualities, including those defined in ISO 4037-1, with first half value layers in the mammographic range. The results indicate that the choice of the radiation quality is not crucial for instruments with a small energy dependence of the response. However, the radiation quality has to be chosen carefully if instruments with a marked dependence of their response to the radiation energy are calibrate

Search for physics beyond the standard model in events with τ leptons, jets, and large transverse momentum imbalance in pp collisions at [Formula: see text].

A search for physics beyond the standard model is performed with events having one or more hadronically decaying τ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at [Formula: see text] collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined

Measurement of K^0_e3 form factors

The semileptonic decay of the neutral K meson, KL -> pi e nu (Ke3), was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector (f_+(q^2)), scalar (f_S) and tensor (f_T) interactions were measured. The linear slope of the vector form factor lambda_+ = 0.0284+-0.0007+-0.0013 and values for the ratios |f_S/f_+(0)| = 0.015^{+0.007}_{-0.010}+-0.012 and |f_T/f_+(0)| = 0.05^{+0.03}_{-0.04}+-0.03 were obtained. The values for f_S and f_T are consistent with zero. Assuming only Vector-Axial vector couplings, lambda_+ = 0.0288+-0.0004+-0.0011 and a good fit consistent with pure V-A couplings were obtained. Alternatively, a fit to a dipole form factor yields a pole mass of M = 859+-18 MeV, consistent with the K^*(892) mass.Comment: 16 pages, 7 figures. submitted to Phys. Lett.

Belle II Technical Design Report

The Belle detector at the KEKB electron-positron collider has collected almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an upgrade of KEKB is under construction, to increase the luminosity by two orders of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2 /s luminosity. To exploit the increased luminosity, an upgrade of the Belle detector has been proposed. A new international collaboration Belle-II, is being formed. The Technical Design Report presents physics motivation, basic methods of the accelerator upgrade, as well as key improvements of the detector.Comment: Edited by: Z. Dole\v{z}al and S. Un

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Latest Results from the Heidelberg-Moscow Double Beta Decay Experiment

New results for the double beta decay of 76Ge are presented. They are extracted from Data obtained with the HEIDELBERG-MOSCOW, which operates five enriched 76Ge detectors in an extreme low-level environment in the GRAN SASSO. The two neutrino accompanied double beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in a half life of (T_(1/2))^(2nu) = [1.55 +- 0.01 (stat) (+0.19) (-0.15) (syst)] x 10^(21) years. The lower limit on the half-life of the 0nu beta-beta decay obtained with pulse shape analysis is (T_(1/2))^(0_nu) > 1.9 x 10^(25) [3.1 x 10^(25)] years with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana neutrino mass of 0.35 eV (0.27 eV). No evidence for a Majoron emitting decay mode or for the neutrinoless mode is observed.Comment: 14 pages, revtex, 6 figures, Talk was presented at third International Conference ' Dark Matter in Astro and Particle Physics' - DARK2000, to be publ. in Proc. of DARK2000, Springer (2000). Please look into our HEIDELBERG Non-Accelerator Particle Physics group home page: http://www.mpi-hd.mpg.de/non_acc