We present the Transition Radiation Detectors (TRD), coupled with the electron trigger, which were designed and built for selecting rare decays of neutral kaons in the KTeV experiment at Fermilab. ...The TRD is a powerful detector for identification of electrons in off-line analysis. A pion-electron rejection factor of 300:1 can be achieved with the KTeV TRD system. The electron trigger also uses signals from the TRD to discriminate electrons on-line. A system of programmable LeCroy 2366 modules runs a pattern recognition algorithm on TRD output with applied pulse height thresholds. A decision on the number of electrons which passed through TRDs is made in less than 500 nanoseconds. A desirable trigger rate suppression or signal efficiency can be achieved by choosing initialization constants for particular experimental conditions. During the experimental run the TRD trigger provided a required trigger rate suppression factor of 1.7-6 with signal efficiency of 97%-85%. In this summary paper we describe briefly the TRD, the main trigger components, and ifs functions. The performance of the TRD and the electron trigger in the KTeV experiment is also summarized.
The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of ...\(30-60\) ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about \(2\times10^{14}\) 1 MeV(Si) Eqv. n/cm\(^2\), that will be integrated over a decade of operation of the High Luminosity Large Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to this level of radiation have shown a strong increase in dark count rate and radiation damage effects that also impact their gain and photon detection efficiency. For this reason during operations the whole detector is cooled down to about \(-35^{\circ}\)C. In this paper we illustrate an innovative and cost-effective solution to mitigate the impact of radiation damage on the timing performance of the detector, by integrating small thermo-electric coolers (TECs) on the back of the SiPM package. This additional feature, fully integrated as part of the SiPM array, enables a further decrease in operating temperature down to about \(-45^{\circ}\)C. This leads to a reduction by a factor of about two in the dark count rate without requiring additional power budget, since the power required by the TEC is almost entirely offset by a decrease in the power required for the SiPM operation due to leakage current. In addition, the operation of the TECs with reversed polarity during technical stops of the accelerator can raise the temperature of the SiPMs up to \(60^{\circ}\)C (about \(50^{\circ}\)C higher than the rest of the detector), thus accelerating the annealing of radiation damage effects and partly recovering the SiPM performance.
To address the challenges of providing high performance calorimetry in future hadron collider experiments under conditions of high luminosity and high radiation (FCChh environments), we are ...conducting R&D on advanced calorimetry techniques suitable for such operation, based on scintillation and wavelength-shifting technologies and photosensor (SiPM and SiPM-like) technology. In particular, we are focusing our attention on ultra-compact radiation hard EM calorimeters, based on modular structures (RADiCAL modules) consisting of alternating layers of very dense absorber and scintillating plates, read out via radiation hard wavelength shifting (WLS) solid fiber or capillary elements to photosensors positioned either proximately or remotely, depending upon their radiation tolerance. The RADiCAL modules provide the capability to measure simultaneously and with high precision the position, energy and timing of EM showers. This paper provides an overview of the instrumentation and photosensor R&D associated with the RADiCAL program.
Phys. Rev. D 100, 032003 (2019) We present a measurement of $B(\pi^0 \rightarrow e^+e^- \gamma)/B(\pi^0
\rightarrow \gamma\gamma)$, the Dalitz branching ratio, using data taken in
1999 by the E832 ...KTeV experiment at Fermi National Accelerator Laboratory. We
use neutral pions from fully reconstructed $K_L$ decays in flight; the
measurement is based on about 60 thousand $K_L \rightarrow \pi^0\pi^0\pi^0
\rightarrow \gamma\gamma~\gamma\gamma~e^+e^-\gamma$ decays. We normalize to
$K_L \rightarrow \pi^0\pi^0\pi^0 \rightarrow 6\gamma$ decays. We find $B(\pi^0
\rightarrow e^+e^- \gamma)/B(\pi^0 \rightarrow \gamma\gamma)$ $(m_{e^+e^-}$ >
15 MeV/$c^2)$ = $3.920 \pm 0.016(stat) \pm 0.036 (syst) \times 10^{-3}$.
Using the Mikaelian and Smith prediction for the $e^+e^-$ mass spectrum, we
correct the result to the full $e^+e^-$ mass range. The corrected result is
$B(\pi^0 \rightarrow e^+e^- \gamma)/B(\pi^0 \rightarrow \gamma\gamma) = 1.1559
\pm 0.0047(stat) \pm 0.0106 (syst)$%. This result is consistent with previous
measurements and the uncertainty is a factor of three smaller than any previous
measurement.
We present a measurement of \(B(\pi^0 \rightarrow e^+e^- \gamma)/B(\pi^0 \rightarrow \gamma\gamma)\), the Dalitz branching ratio, using data taken in 1999 by the E832 KTeV experiment at Fermi ...National Accelerator Laboratory. We use neutral pions from fully reconstructed \(K_L\) decays in flight; the measurement is based on about 60 thousand \(K_L \rightarrow \pi^0\pi^0\pi^0 \rightarrow \gamma\gamma~\gamma\gamma~e^+e^-\gamma\) decays. We normalize to \(K_L \rightarrow \pi^0\pi^0\pi^0 \rightarrow 6\gamma\) decays. We find \(B(\pi^0 \rightarrow e^+e^- \gamma)/B(\pi^0 \rightarrow \gamma\gamma)\) \((m_{e^+e^-}\) > 15 MeV/\(c^2)\) = \(3.920 \pm 0.016(stat) \pm 0.036 (syst) \times 10^{-3}\). Using the Mikaelian and Smith prediction for the \(e^+e^-\) mass spectrum, we correct the result to the full \(e^+e^-\) mass range. The corrected result is \(B(\pi^0 \rightarrow e^+e^- \gamma)/B(\pi^0 \rightarrow \gamma\gamma) = 1.1559 \pm 0.0047(stat) \pm 0.0106 (syst)\)%. This result is consistent with previous measurements and the uncertainty is a factor of three smaller than any previous measurement.
PDF
