45,311 research outputs found
From vertex detectors to inner trackers with CMOS pixel sensors
The use of CMOS Pixel Sensors (CPS) for high resolution and low material
vertex detectors has been validated with the 2014 and 2015 physics runs of the
STAR-PXL detector at RHIC/BNL. This opens the door to the use of CPS for inner
tracking devices, with 10-100 times larger sensitive area, which require
therefore a sensor design privileging power saving, response uniformity and
robustness. The 350 nm CMOS technology used for the STAR-PXL sensors was
considered as too poorly suited to upcoming applications like the upgraded
ALICE Inner Tracking System (ITS), which requires sensors with one order of
magnitude improvement on readout speed and improved radiation tolerance. This
triggered the exploration of a deeper sub-micron CMOS technology, Tower-Jazz
180 nm, for the design of a CPS well adapted for the new ALICE-ITS running
conditions. This paper reports the R&D results for the conception of a CPS well
adapted for the ALICE-ITS.Comment: 4 pages, 4 figures, VCI 2016 conference proceeding
Isolated vacua in supersymmetric Yang-Mills theories
An explicit proof of the existence of nontrivial vacua in the pure
supersymmetric Yang-Mills theories with higher orthogonal SO(N), N>=7 or the
G_2 gauge group defined on a 3-torus with periodic boundary conditions is
given. Extra vacuum states are separated by an energy barrier from the
perturbative vacuum A_i=0 and its gauge copies.Comment: 8 pages, no figures, late
Gauge Invariance and the Pauli-Villars Regulator in Lorentz- and CPT-Violating Electrodynamics
We examine the nonperturbative structure of the radiatively induced
Chern-Simons term in a Lorentz- and CPT-violating modification of QED. Although
the coefficient of the induced Chern-Simons term is in general undetermined,
the nonperturbative theory appears to generate a definite value. However, the
CPT-even radiative corrections in this same formulation of the theory generally
break gauge invariance. We show that gauge invariance may yet be preserved
through the use of a Pauli-Villars regulator, and, contrary to earlier
expectations, this regulator does not necessarily give rise to a vanishing
Chern-Simons term. Instead, two possible values of the Chern-Simons coefficient
are allowed, one zero and one nonzero. This formulation of the theory therefore
allows the coefficient to vanish naturally, in agreement with experimental
observations.Comment: 8 page
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