6,122 research outputs found
Performance verification of the CMS Phase-1 Upgrade Pixel detector
The CMS tracker consists of two tracking systems utilizing semiconductor
technology: the inner pixel and the outer strip detectors. The tracker
detectors occupy the volume around the beam interaction region between 3 cm and
110 cm in radius and up to 280 cm along the beam axis. The pixel detector
consists of 124 million pixels, corresponding to about 2 m total area. It
plays a vital role in the seeding of the track reconstruction algorithms and in
the reconstruction of primary interactions and secondary decay vertices. It is
surrounded by the strip tracker with 10 million read-out channels,
corresponding to 200 m total area. The tracker is operated in a
high-occupancy and high-radiation environment established by particle
collisions in the LHC. The performance of the silicon strip detector continues
to be of high quality. The pixel detector that has been used in Run 1 and in
the first half of Run 2 was, however, replaced with the so-called Phase-1
Upgrade detector. The new system is better suited to match the increased
instantaneous luminosity the LHC would reach before 2023. It was built to
operate at an instantaneous luminosity of around
210cms. The detector's new layout has an
additional inner layer with respect to the previous one; it allows for more
efficient tracking with smaller fake rate at higher event pile-up. The paper
focuses on the first results obtained during the commissioning of the new
detector. It also includes challenges faced during the first data taking to
reach the optimal measurement efficiency. Details will be given on the
performance at high occupancy with respect to observables such as data-rate,
hit reconstruction efficiency, and resolution.Comment: 11 pages, 8 figures, 11th International Conference of Position
Sensitive Detectors (PSD11
Radiation experience with the CMS pixel detector
The CMS pixel detector is the innermost component of the CMS tracker
occupying the region around the centre of CMS, where the LHC beams are crossed,
between 4.3 cm and 30 cm in radius and 46.5 cm along the beam axis. It operates
in a high-occupancy and high-radiation environment created by particle
collisions. Studies of radiation damage effects to the sensors were performed
throughout the first running period of the LHC. Leakage current, depletion
voltage, pixel readout thresholds, and hit finding efficiencies were monitored
as functions of the increasing particle fluence. The methods and results of
these measurements will be described together with their implications to
detector operation as well as to performance parameters in offline hit
reconstruction.Comment: 10 pages, 11 figures, conference proceedings for International
Workshop on Semiconductor Pixel Detectors for Particles and Imaging
(PIXEL2014), elaborates on one section of arXiv:1402.0675; Corrected typo
Measurement of the Dipion Mass Spectrum in X(3872) -> J/Psi Pi+ Pi- Decays
We measure the dipion mass spectrum in X(3872)--> J/Psi Pi+ Pi- decays using
360 pb-1 of pbar-p collisions at 1.96 TeV collected with the CDF II detector.
The spectrum is fit with predictions for odd C-parity (3S1, 1P1, and 3DJ)
charmonia decaying to J/Psi Pi+ Pi-, as well as even C-parity states in which
the pions are from Rho0 decay. The latter case also encompasses exotic
interpretations, such as a D0-D*0Bar molecule. Only the 3S1 and J/Psi Rho
hypotheses are compatible with our data. Since 3S1 is untenable on other
grounds, decay via J/Psi Rho is favored, which implies C=+1 for the X(3872).
Models for different J/Psi-Rho angular momenta L are considered. Flexibility in
the models, especially the introduction of Rho-Omega interference, enable good
descriptions of our data for both L=0 and 1.Comment: 7 pages, 4 figures -- Submitted to Phys. Rev. Let
- …