118498165
Prediction of Underground Argon Content for Dark Matter Experiments
In this paper, we demonstrate the use of physical models to evaluate the production of $^{39}\mathrm{Ar}$ and $^{40}\mathrm{Ar}$ underground. Considering both cosmogenic $^{39}\mathrm{Ar}$ production and radiogenic $^{40}\mathrm{Ar}$ production in situ and from external sources, we can derive the ratio of $^{39}\mathrm{Ar}$ to $^{40}\mathrm{Ar}$ in underground sources. We show for the first time that the $^{39}\mathrm{Ar}$ production underground is dominated by stopping negative muon capture on $^{39}\mathrm{K}$ and ($\ensuremath{\alpha},n)$ induced subsequent $^{39}\mathrm{K}$($n$,$p$)$^{39}\mathrm{Ar}$ reactions. The production of $^{39}\mathrm{Ar}$ is shown as a function of depth. We demonstrate that argon depleted in $^{39}\mathrm{Ar}$ can be obtained only if the depth of the underground resources is greater than $500$ m.w.e. below the surface. Stopping negative muon capture on $^{39}\mathrm{K}$ dominates over radiogenic production at depths of less than $2000$ m.w.e., and that production by muon-induced neutrons is subdominant at any depth. The depletion factor depends strongly on both radioactivity level and potassium content in the rock. We measure the radioactivity concentration and potassium concentration in the rock for a potential site of an underground argon source in South Dakota. Depending on the probability of $^{39}\mathrm{Ar}$ and $^{40}\mathrm{Ar}$ produced underground being dissolved in the water, the upper limit of the concentration of $^{39}\mathrm{Ar}$ in the underground water at this site is estimated to be in a range of a factor of $1.6$ to $155$ less than the $^{39}\mathrm{Ar}$ concentration in the atmosphere. The calculation tools presented in this paper are also critical to the dating method with $^{39}\mathrm{Ar}$.
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.
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.
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 .
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.
6748343
Mirror Symmetry in Three-Dimensional Gauge Theories, SL(2, Z) and D-Brane Moduli Spaces
We construct intersecting D-brane configurations that encode the gauge groups and field content of dual N = 4 supersymmetric gauge theories in three dimensions. The duality which exchanges the Coulomb and Higgs branches and the Fayet-Iliopoulos and mass parameters is derived from the SL (2, Z) symmetry of the type IIB string. Using the D-brane configurations we construct explicitly this mirror map between the dual theories and study the instanton corrections in the D-brane world-volume theory via open string instantons. A general procedure to obtain mirror pairs is presented and illustrated. We encounter transitions among different field theories that correspond to smooth movements in the D-brane moduli space. We discuss the relation between the duality of the gauge theories and the level-rank duality of affine Lie algebras. Examples of other dual theories are presented and explained via T-duality and extremal transitions in type II string compactifications. Finally we discuss a second way to study instanton corrections in the gauge theory, by wrapping 5-branes around six-cycles in M-theory compactified on a Calabi-Yau 4-fold.
10041169
Conformal invariance on orbifolds and excitations of singularity
We study conformal field theory on two-dimensional orbifolds and show this to be an effective way to analyze physical effects of geometric singularities with angular deficits. They are closely related to boundaries and cross caps. Representative classes of singularities can be described exactly using generalizations of boundary states. From this we compute correlation functions and derive the spectra of excitations localized at the singularities.
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.
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.