We present a search for a non-Standard-Model invisible particle X0 in the mass range 0.1-1.8GeV/c2 in B+→e+X0 and B+→μ+X0 decays. The results are obtained from a 711 fb-1 data sample that corresponds ...to 772×106BB pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB e+e- collider. One B meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner B meson. We find no evidence of a signal and set upper limits on the order of 10-6.
The use of a sequence of aerogel radiators with different refractive indices in a proximity focusing Cherenkov ring imaging detector has been shown to improve the resolution of the Cherenkov angle. ...In order to obtain further information on the capabilities of such a detector, a maximum-likelihood analysis has been performed on simulated data, with the simulation being appropriate for the upgraded Belle detector. The results show that by using a sequence of two aerogel layers with different refractive indices, the
K
/
π
separation efficiency is improved in the kinematic region above 3
GeV/
c. In the low momentum region, the focusing configuration (with
n
1
and
n
2
chosen such that the Cherenkov rings from different aerogel layers at 4
GeV/
c overlap) shows a better performance than the defocusing one (where the two Cherenkov rings are well separated).
Test of the Hamamatsu MPPC module S11834 as a RICH photon detector Korpar, S.; Tahirović, E.; Križan, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2014, Letnik:
766
Journal Article
Recenzirano
In our previous studies, we have shown that silicon photo-multipliers can be used as single photon detectors in a RICH counter (Korpar et al., 2009, 2010 1 and 2). Their main advantage with respect ...to the classical photo-multiplier tubes is the operation in high magnetic fields, while their disadvantage is a relatively high dark count rate. Recently, Hamamatsu made commercially available sensors with a rather low dark count rate ( approximately 0.1 MHz/mm super(2)) and with a larger active area, offering a possibility for a much better signal-to-noise ratio. We have designed, constructed and tested a module with Hamamatsu 88 channel S11834 MPPCs. To increase the geometric acceptance, light concentrators have been employed. In the present contribution we discuss the results of studies of the light concentrator design optimization and of the detector module response to fast light pulses. Also presented are the results of RICH prototype tests in a test beam.
Silicon photo-multipliers as photon detectors for PET Pestotnik, R.; Korpar, S.; Chagani, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2010, Letnik:
623, Številka:
1
Journal Article
Recenzirano
A novel photon detector, the Silicon Photomultiplier (SiPM), has been tested in view of a photosensitive device for Positron Emission Tomography (PET), which is one of the most important non-invasive ...methods for in-depth and in vivo imaging of tissue. Such a device offers advantages over existing ones, including application in a magnetic field, better resolution and easier operation. Two PET modules have been constructed by coupling an array of Hamamatsu 3mm×3mm Multi-pixel photon Counters (MPPCs) and Photonique 2.2mm×2.2mm Solid-state Photomultipliers (SSPMs) to LYSO scintillation crystals. The results of studies of the two module prototypes are presented.
The cross section for e(+)e(-)-->pi(+)pi(-)J/psi between 3.8 and 5.5 GeV/c(2) is measured using a 548 fb(-1) data sample collected on or near the Upsilon(4S) resonance with the Belle detector at ...KEKB. A peak near 4.25 GeV/c(2), corresponding to the so called Y(4260), is observed. In addition, there is another cluster of events at around 4.05 GeV/c(2). A fit using two interfering Breit-Wigner shapes describes the data better than one that uses only the Y(4260), especially for the lower-mass side of the 4.25 GeV enhancement.
The cross section for e+ e- --> pi+ pi- psi(2S) between threshold and sqrts=5.5 GeV is measured using 673 fb(-1) of data on and off the Upsilon(4S) resonance collected with the Belle detector at ...KEKB. Two resonant structures are observed in the pi+ pi- psi(2S) invariant-mass distribution, one at 4361 +/- 9 +/- 9 MeV/c2 with a width of 74 +/- 15 +/- 10 MeV/c2, and another at 4664 +/- 11 +/- 5 MeV/c2 with a width of 48 +/- 15 +/- 3 MeV/c2, if the mass spectrum is parametrized with the coherent sum of two Breit-Wigner functions. These values do not match those of any of the known charmonium states.
We present a search for lepton-flavor-violating τ decays into three leptons (electrons or muons) using 782 fb−1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e− collider. ...No evidence for these decays is observed and we set 90% confidence level upper limits on the branching fractions between 1.5×10−8 and 2.7×10−8.
Silicon photomultiplier as a detector of Cherenkov photons Korpar, S.; Dolenec, R.; Hara, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2008, Letnik:
595, Številka:
1
Journal Article
Recenzirano
A novel photon detector—i.e. the silicon photomultiplier—whose main advantage over conventional photomultiplier tubes is the operation in high magnetic fields, has been tested as a photon detector in ...a proximity focusing RICH with aerogel radiator. This type of RICH counter is proposed for the upgrade of the Belle detector at the KEK B-factory. Recently produced silicon photomultipliers show less noise and have larger size, which are important issues for a large area photon detector. We measured the single photon pulse height distribution, the timing resolution and the position sensitivity for different silicon photomultipliers (Hamamatsu MPPC HC025, HC050, and HC100). The silicon photomultipliers were then used to detect Cherenkov photons emitted by cosmic ray particles in a proximity focusing aerogel RICH. Various light guides were investigated in order to increase the detection efficiency.
Measurement of Cherenkov photons with silicon photomultipliers Korpar, S.; Dolenec, R.; Hara, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2008, Letnik:
594, Številka:
1
Journal Article
Recenzirano
In addition to their other advantages, silicon photomultipliers (SiPMs) are insensitive to magnetic fields, so they would be attractive as photon detectors for ring imaging Cherenkov counters inside ...large magnetic spectrometers. In view of the foreseen upgrade of the particle identification system of the Belle spectrometer, we have investigated the possibilities offered by these new photon detectors. Cherenkov photons emitted by cosmic ray particles in an aerogel radiator have been detected with SiPMs for the first time. Estimates and tests show that light concentrators may improve the detection efficiency, thus showing promise for an SiPM based RICH detector.
PDF
