[Show abstract][Hide abstract] ABSTRACT: This work is on the Physics of the B Factories. Part A of this book contains
a brief description of the SLAC and KEK B Factories as well as their detectors,
BaBar and Belle, and data taking related issues. Part B discusses tools and
methods used by the experiments in order to obtain results. The results
themselves can be found in Part C.
Please note that version 3 on the archive is the auxiliary version of the
Physics of the B Factories book. This uses the notation alpha, beta, gamma for
the angles of the Unitarity Triangle. The nominal version uses the notation
phi_1, phi_2 and phi_3. Please cite this work as Eur. Phys. J. C74 (2014) 3026.
European Physical Journal C 11/2014; DOI:10.1140/epjc/s10052-014-3026-9 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The present B factories, running at the luminosity of , have established a large time-dependent CP asymmetry in B decays. Upgrade of the KEKB accelerator to a luminosity of , designated Super KEKB, has been proposed to extend physics reach beyond the standard model. Since measurement of time evolution of B mesons is essential, the silicon vertex detector, SVD, should be redesigned to meet the data rates and radiation backgrounds expected in this Super KEKB environment. The detector configuration, sensor options and read out electronics are discussed.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2005; DOI:10.1016/j.nima.2005.01.084 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Silicon Vertex Detector (SVD) of the Belle experiment is one of the main components for the investigation of time-dependent CP-asymmetries at the B-factory at KEK. The first version of this device (SVD1) was operated for 4 years starting in 1999 with excellent performance. However, its major limitations necessitated the design of a new detector (SVD2) which was installed in the summer shutdown of 2003. The improvements of the hardware and first results on the performance under real beam conditions are presented.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2005; DOI:10.1016/j.nima.2005.01.038 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A major upgrade of the Silicon Vertex Detector (SVD 2.0) of the Belle experiment at the KEKB factory was installed along with new front-end and back-end electronics systems during the summer shutdown period in 2003 to cope with higher particle rates, improve the track resolution and meet the increasing requirements of radiation tolerance. The SVD 2.0 detector modules are read out by VA1TA chips which provide "fast or" (hit) signals that are combined by the back-end FADCTF modules to coarse, but immediate level 0 track trigger signals at rates of several tens of a kHz. Moreover, the digitized detector signals are compared to threshold lookup tables in the FADCTFs to pass on hit information on a single strip basis to the subsequent level 1.5 trigger system, which reduces the rate below the kHz range. Both FADCTF and level 1.5 electronics make use of parallel real-time processing in Field Programmable Gate Arrays (FPGAs), while further data acquisition and event building is done by PC farms running Linux. The new readout system hardware is described and the first results obtained with cosmics are shown.
10th International Vienna Conference on Instrumentation; 12/2004
[Show abstract][Hide abstract] ABSTRACT: We have upgraded the beampipe and the silicon vertex tracker of the Belle detector for increased luminosity and to achieve better vertex resolution. The radius of the beampipe was reduced from 2 to 1.5 cm to achieve better vertex resolution. In order to reduce the beam background that could accompany the reduction of the beampipe radius, a massive mask made of tantalum and tungsten was placed on each side of the central section. The total weight of them is 40 kg. The maximum radiation dose of the silicon tracker is measured about 80 krad/yr. This is lower than the dose of 100 krad per year with the previous beampipe even though the beampipe radius is smaller. The beampipe is designed to minimize heating, and enough cooling power is provided by the liquid cooling.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2004; DOI:10.1016/j.nima.2004.07.260 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new silicon vertex detector for the BELLE experiment was installed and its operation has started successfully at the high-luminosity asymmetric energy e(+)e(-) collider KEKB in October 2003. This vertex detector provides a larger polar angle acceptance, a more precise vertex resolution and a better radiation tolerance than the previous one. The obtained performances indicate that the SVD2 works reliably as expected. Moreover, a prospective simulation study shows that the SVD2 should work under the coming higher background conditions. (C) 2004 Published by Elsevier B.V.
10th International Vienna Conference on Instrumentation; 12/2004
[Show abstract][Hide abstract] ABSTRACT: We report evidence for direct CP violation in the decay B0-->K+pi(-) with 253 fb(-1) of data collected with the Belle detector at the KEKB e(+)e(-) collider. Using 275x10(6) BB pairs we observe a B-->K+/-pi(-/+) signal with 2140+/-53 events. The measured CP violating asymmetry is A(CP)(K+pi(-))=-0.101+/-0.025(stat)+/-0.005(syst), corresponding to a significance of 3.9sigma including systematics. We also search for CP violation in the decays B+-->K+pi(0) and B+-->pi(+)pi(0). The measured CP violating asymmetries are A(CP)(K+pi(0))=0.04+/-0.05(stat)+/-0.02(syst) and A(CP)(pi(+)pi(0))=-0.02+/-0.10(stat)+/-0.01(syst), corresponding to the intervals -0.05<A(CP)(K+pi(0))<0.13 and -0.18<A(CP)(pi(+)pi(0))<0.14 at 90% confidence level.
[Show abstract][Hide abstract] ABSTRACT: A newly developed data acquisition system (DAQ) for the upgraded silicon vertex detector (SVD2) in the Belle experiment is described. The system consists of 12 PCs connected through PCI I/O boards to 36 flash analog-to-digital converters (FADCs) to read out a system comprising a total of 110 592 strips. It is designed to cope with the increased number of readout channels and the maximum trigger rate of 1 kHz, foreseen in the future operation with higher beam currents. A measurement of the system performance using sparsification algorithm we have developed yields a 1.3-kHz readout rate for a 5% occupancy with less than 5% dead time, which satisfies the requirements on the maximum trigger rate.
[Show abstract][Hide abstract] ABSTRACT: During the summer shutdown of 2003, the new silicon vertex detector SVD2 was installed in Belle at the KEKB factory and started to take data in October 2003. It provides important improvements in the tracking capabilities and adds new trigger functionality. In addition, a new hardware trigger Level 1.5 was designed and installed that takes advantage of the digitized SVD hit data. The improvement in the Belle trigger system will be important to deal with the increasing luminosity and higher beam currents of the KEKB factory.
[Show abstract][Hide abstract] ABSTRACT: The evidence for direct charged particles (CP) violation in the decay B0→K+ π- was investigated with 253 fb-1 of data collected with the Belle detector at the KEKB e + e- collider. 275 x 106 BB̄ pairs were used to observe a B→K±π∓ signal with 2140 ±53 events. Mixing induced CP violation in the B sector was established in b → cc̄s transitions. The result suggests large interference between tree and penguin diagrams and the existence of final state interactions.
[Show abstract][Hide abstract] ABSTRACT: We present an improved measurement of CP-violating asymmetries in B0→π+π- decays based on a 78fb-1 data sample collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one neutral B meson as a B0→π+π- CP eigenstate and identify the flavor of the accompanying B meson from inclusive properties of its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes Aππ=+0.77±0.27(stat)±0.08(syst) and Sππ=-1.23±0.41(stat)-0.07+0.08(syst), where the statistical uncertainties are determined from the Monte Carlo pseudoexperiments. We obtain confidence intervals for CP-violating asymmetry parameters Aππ and Sππ based on a frequentist approach. We rule out the CP-conserving case, Aππ=Sππ=0, at the 99.93% confidence level. We discuss how these results constrain the value of the Cabibbo-Kobayashi-Maskawa (CKM) angle φ2.
[Show abstract][Hide abstract] ABSTRACT: The branching fraction for the inclusive decay Β→Xsℓ+ℓ- was measured. A data sample collected at the Υ(4S) resonance with the Bell detector at the KEKB e+e- asymmetric-energy collider was used. Overall, the results are in agreement with the standard model (SM) expectations and can be used to constrain extensions of the SM.
[Show abstract][Hide abstract] ABSTRACT: We report the first measurement of the branching fraction for the inclusive decay B-->Xsl+l-, where l is either an electron or a muon, and Xs is a hadronic recoil system that contains an s quark. We analyzed a data sample of 65.4×106 B meson pairs collected with the Belle detector at the KEKB e+e- asymmetric-energy collider. We find B(B-->Xsl+l-)=[6.1 ±1.4(stat) +1.4-1.1(syst)]×10-6 for dilepton masses greater than 0.2 GeV/c2.
[Show abstract][Hide abstract] ABSTRACT: We report the first measurement of the branching fraction for the inclusive decay B-->X(s)l(+)l(-), where l is either an electron or a muon, and X(s) is a hadronic recoil system that contains an s quark. We analyzed a data sample of 65.4 x 10(6) B meson pairs collected with the Belle detector at the KEKB e(+)e(-) asymmetric-energy collider. We find B(B-->X(s)l(+)l(-))=[6.1 +/-1.4(stat) +1.4-1.1(syst)] x 10(-6) for dilepton masses greater than 0.2 GeV/c(2).