7829180
The BRAHMS ring imaging Cherenkov detector
Abstract A Ring Imaging Cherenkov detector built for the BRAHMS experiment at the Brookhaven RHIC is described. This detector has a high index of refraction gas radiator. Cherenkov light is focused on a photo-multiplier based photon detector with a large spherical mirror. The combination of momentum and ring radius measurement provides particle identification from 2.5 to 35 GeV/ c for pions and kaons and well above 40 GeV/ c for protons during runs that had the radiator index of refraction set at n - 1 = 1700 × 10 - 6 .
120878684
Important observables from the BRAHMS experiment
We present the important observables from the BRAHMS experiment for establishing the properties of the hot and dense strongly interacting QCD matter with respect to its formation, evolution and its effects on high p Tparticle production.
122716775
Elliptic flow of strange and multi-strange particles in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76-TeV measured with ALICE
108585326
Trigger electronics for the Alice PHOS detector
Abstract The Photon Spectrometer of ALICE consists of 5 identical modules of 56×64 PWO crystals with a total of 100° azimuthal coverage of the barrel. The electronics required for implementing both the L0 trigger for high luminosity p–p physics and the L1 trigger for high p T Pb+Pb physics has been studied. A full integration of the trigger logic into the detector's enclosure is based on analog transmission of fast trigger sums between stacks of front-end boards and trigger-router units. The latter contain 112 digitizer channels of 10 bit, which are mapped into a single FPGA per trigger unit, covering areas of 24×16 crystals. The running modes allow for Level-0 trigger at 800 ns and Level-1 at 6200 ns trigger latencies. The design and status of the PHOS trigger electronics are outlined.
121970317
Charged particle identification with PHOS and central tracking of ALICE
The ALICE Photon Spectrometer (PHOS) has been designed to measure the photon spectrum produced in pp and AA collisions at LHC over a broad transverse momentum range from 0.5–100 GeV/c. We present a study on the matching of charged tracks, detected by the ALICE central tracking detectors, with clusters of hit PHOS elements. Matching efficiency and contamination due to false matches have been deduced for charged pions, muons and electrons. The study indicates also that material from other detectors in front of PHOS disturbs the photon detection.
110904443
Configurable electronics with low noise and 14-bit dynamic range for photodiode-based photon detectors
Abstract We describe the principles and measured performance of custom configurable 32-channel shaper/digitizer Front End Electronics (FEE) cards with 14-bit dynamic range for gain-adjustable photon detectors. The electronics has been designed for the PHOS calorimeter of ALICE with avalanche photodiode (APD) readout operated at −25 °C ambient temperature and a signal shaping time of 1 μs. The electronics has also been adopted by the EMCal detector of ALICE with the same APD readout, but operated at an ambient temperature of +20 °C and with a shaping time of 100 ns. The CR-RC2 signal shapers on the FEE cards are implemented in discrete logic on a 10-layer board with two shaper sections for each input channel. The two shaper sections with gain ratio of 16:1 are digitized by 10-bit ADCs and provide an effective dynamic range of 14 bits. Gain adjustment for each individual APD is available through 32 bias voltage control registers of 10-bit range. The fixed gains and shaping times of the pole-zero compensated shapers are defined prior to FEE production by the values of a few R and C components. For trigger purposes, “fast OR” outputs with 12-bit dynamic range are available. FPGA based slave logic, combined with a USB processor supports a variety of remote control and monitoring features, including APD gain calibration. The measurements presented here for APDs at −25 °C ambient temperature and 1 μs shaping time achieve an average RMS noise level of 0.25 ADC counts or 290 electrons.The linearity over the dynamic range is better than 1%, as is the uniformity of shaping time and gain over 32 channels. Due to the excellent correspondence of the output pulse shape with offline fit, a differential timing resolution of less than 1.5 ns between channels has been achieved at ca. 2 GeV, i.e. at 1.5% of the dynamic range of PHOS.
17895994
TASI Lectures on Perturbative String Theories
These lecture notes are based on a course on string theories given by Hirosi Ooguri in the first week of TASI 96 Summer School at Boulder, Colorado. It is an introductory course designed to provide students with minimum knowledge before they attend more advanced courses on non-perturbative aspects of string theories in the School. The course consists of five lectures: 1. Bosonic String, 2. Toroidal Compactifications, 3. Superstrings, 4. Heterotic Strings, and 5. Orbifold Compactifications.
9218563
A note on space noncommutativity
Abstract We consider a two-point spatial lattice approximation to an open string moving in a flat background with B field. It gives a constrained dipole system under the influence of a vector potential. Solving and quantizing this system recover all the essential features of a noncommutative space. In particular, open string interactions induce a canonical product structure on the Hilbert space of the dipole system. It coincides with the usual star product, even though the position operators can be thought of as mutually commuting. Modification of gauge transformations in this noncommutative space also naturally emerges.
17461222
The principle of least action and the geometric basis of D-branes
We analyze thoroughly the boundary conditions allowed in classical non-linear sigma models and derive from first principle the corresponding geometric objects, i.e. D-branes. In addition to giving classical D-branes an intrinsic and geometric foundation, D-branes in nontrivial H flux and D-branes embedded within D-branes are precisely defined. A well known topological condition on D-branes is replaced.
15652578
Mirrors and Phases of N=4 in D=3
3d mirror symmetry for was first proposed in [1] as a duality between certain pairs of generally different 3d N=4 theories at the infrared limit. Infinite sequences of new mirror pairs and strong field theoretic evidence for them were found in [2]. It is a nonperturbative duality that in particular equates certain quantities receiving large quantum corrections with some that are determined entirely classically. Naturally one asks whether this can be the consequence of some string dualities. There are several different approaches [1, 2, 3, 4, 5, 6, 7], each of which has it own advantage and is related to the others by some sequences of dualities. In this talk I will review one that is particularly intuitive [4, 5]. The global R-symmetry of N=4 theories appears as geometric rotations; R-symmetry breaking part of the moduli space of vacua and the parameters of the field theory are realized as the moduli space of D-branes configurations; mirror symmetry itself is implemented by the S duality of type IIB string theory [4]. This construction allows us to engineer a large class of theories and find their mirror duals [5]. Since then it has been generalized to 3d N=2 theories [8, 9]. Similar ideas of constructing field theories in 4d, reviewed in Eguchi’s lecture at this school [10], have also been very fruitful1. In this talk, I will focus on 3d N=4 theories. After reviewing the rules for “model building” via “brane engineering,” I will show how the mirror pairs emerge from this prescription. As an unexpected reward we can predict an infinite number of 3d field theories without conventional Lagrangian descriptions. Some of them are dual to ordinary Lagrangian theories via mirror symmetry, but the rest are not; yet they can be smoothly connected in the moduli space of brane configurations.
651025
D-branes on Calabi-Yau spaces and their mirrors
We study the boundary states of D-branes wrapped around supersymmetric cycles in a general Calabi-Yau manifold. In particular, we show how the geometric data on the cycles are encoded in the boundary states. As an application, we analyze how the mirror symmetry transforms D-branes, and we verify that it is consistent with the conjectured periodicity and the monodromy of the Ramond-Ramond field configuration on a Calabi-Yau manifold. This also enables us to study open string worldsheet instanton corrections and relate them to closed string instanton counting. The cases when the mirror symmetry is realized as T-duality are also discussed.