118604753
Strange and multi-strange particle production in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE
We present ALICE results on strange and multi-strange hadron production as a function of centrality in Pb-Pb collisions at $\sqrt{s_{{\rm NN}}} = 2.76~{\rm TeV}$ at the LHC. Their transverse momentum spectra, yields and particle ratios are compared to the corresponding measurements in pp collisions to address strangeness enhancement and high pT particle suppression. The results are also compared to measurements at RHIC and SPS energies.
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
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.
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.
15577760
From boundaries to conditions over superspace
N = 1 and 2 superconformal boundary conditions are shown to be the consequence of a ``boundary'' on the worldsheet superspace with positive codimension in the anticommuting subspace. In addition to the well-known boundary conditions, I also find two new infinite series of N = 2 boundary states. Their free field realizations are given. A self-contained development of 2d superspace leads to new perspectives on this subject.
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.
14412974
Families of N=2 strings
In a given 4d spacetime bakcground, one can often construct not one but a family of distinct N = 2 string theories. This is due to the multiple ways an N = 2 superconformal algebra can be embedded in a given worldsheet theory. We formulate the principle of obtaining different physical theories by gauging different embeddings of the same symmetry algebra in the same "pre-theory." We then apply it to the N = 2 strings and formulate the recipe for finding the associated parameter spaces of gauging. Flat and curved target spaces of both (4,0) and (2,2) signatures are considered. We broadly divide the gauging choices into two classes, denoted by α and β, and show them to be related by T-duality. The distinction between them is formulated topologically and hinges on some unique properties of 4d manifolds. We determine what their parameter spaces of gauging are under certain simplicity ansatz for generic flat spaces (4 and its toroidal compactifications) as well as some curved spaces. We briefly discuss the spectra of D-branes for both α and β families.
5633727
Anomalies, Branes, and Currents
Abstract When a D-brane wraps around a cycle of a curved manifold, the twisting of its normal bundle can induce chiral asymmetry in its world-volume theory. We obtain the general form of the resulting anomalies for D-branes and their intersections. They are not cancelled among themselves, and the standard inflow mechanism does not apply at first sight because of their apparent lack of factorizability and the apparent vanishing of the corresponding inflow. We show, however, that after taking into consideration the effects of the non-trivial topology of the normal bundles, the anomalies can be transformed into factorized forms and precisely cancelled by finite inflow from the Chern-Simons actions for the D-branes as long as the latter are well defined. We then consider examples in type 11 compactifications where the twisting of the normal bundles occurs and calculate the changes in the induced Ramond-Ramond charges on the D-branes.
10027781
SUPERSYMMETRIC CYCLES IN EXCEPTIONAL HOLONOMY MANIFOLDS AND CALABI-YAU FOUR-FOLDS
We derive in the SCFT and low energy effective action frameworks the necessary and sufficient conditions for supersymmetric cycles in exceptional holonomy manifolds and Calabi-Yau four-folds. We show that the Cayley cycles in Spin(7) holonomy eight-manifolds and the associative and coassociative cycles in G2 holonomy seven-manifolds preserve half of the space-time supersymmetry. We find that while the holomorphic and special Lagrangian cycles in Calabi-Yau four-folds preserve half of the space-time supersymmetry, the Cayley submanifolds are novel as they preserve only one quarter of it. We present some simple examples. Finally, we discuss the implications of these supersymmetric cycles on mirror symmetry in higher dimensions.