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Register a new userSTAR Barrel Electromagnetic Calorimeter Absolute Calibration Using Minimum Ionizing Particles from Collisions at RHIC
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The procedure for the STAR Barrel Electromagnetic Calorimeter (BEMC) absolute calibrations, using penetrating charged particle hits (MIP-hits) from physics events at RHIC, is presented. Its systematic and statistical errors are evaluated. It is shown that, using this technique, the equalization and transfer of the absolute scale from the test beam can be done to a percent level accuracy in a reasonable amount of time for the entire STAR BEMC. MIP-hits would also be an effective tool for continuously monitoring the variations of the BEMC towers gains, virtually without interference to STARs main physics program. The method does not rely on simulations for anything other than geometric and some other small corrections, and also for estimations of the systematic errors. It directly transfers measured test beam responses to operations at RHIC.
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We derive a new method to improve the statistics of identified particles at high transverse momentum (pt) using online-triggered events by the Barrel Electro-Magnetic-Calorimeter (BEMC) detector. The BEMC is used to select hadronic interaction and energy deposit from showers created by charged hadrons ($pi^{pm},K^{pm}$ and $p$($bar{p}$)) in the BEMC. With this trigger, the statistics of the high pt particles are significantly enhanced by about a factor of 100 with selection efficiency up to 20%. In addition, resonant states ($rho^0$, $K^{star}$) and weak-decay V0 (Ks and La(aLa)) can be constructed by selecting the BEMC-trigger hadron as one of its daughters. We also show that the trigger efficiency can be obtained reliably in simulation and data-driven approaches.
Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy of $Delta P_{beam}/P_{beam} < 5%$. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features textit{proton-proton} elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power $A_N$ of this process has allowed us to achieve $Delta P_{beam}/P_{beam} =4.2%$ in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of $A_N$ in the CNI region (four-momentum transfer squared $0.001 < -t < 0.032 ~ ({rm GeV}/c)^2$) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.
The e/$pi$ ratio for the Barrel Combined Calorimeter Prototype, composed from electromagnetic LAr calorimeter and hadronic Tile calorimter was investigated. Response of Combined Calorimeter on pions and electrons in the energy region 20 - 300 GeV was studied. Found $e/h = 1.37pm0.01pm0.02$ is in good agreement with results from previous Combined Calorimeter test but has more precisions.
The Cryogenic Dark Matter Search low ionization threshold experiment (CDMSlite) achieved efficient detection of very small recoil energies in its germanium target, resulting in sensitivity to Lightly Ionizing Particles (LIPs) in a previously unexplored region of charge, mass, and velocity parameter space. We report first direct-detection limits calculated using the optimum interval method on the vertical intensity of cosmogenically-produced LIPs with an electric charge smaller than $e/(3times10^5$), as well as the strongest limits for charge $leq e/160$, with a minimum vertical intensity of $1.36times10^{-7}$,cm$^{-2}$s$^{-1}$sr$^{-1}$ at charge $e/160$. These results apply over a wide range of LIP masses (5,MeV/$c^2$ to 100,TeV/$c^2$) and cover a wide range of $betagamma$ values (0.1 -- $10^6$), thus excluding non-relativistic LIPs with $betagamma$ as small as 0.1 for the first time.
Sufficient energy resolution is the key issue for the calorimetry in particle and nuclear physics. The calorimeter of the A4 parity violation experiment at MAMI is a segmented calorimeter where the energy of an event is determined by summing the signals of neighbouring channels. In this case the precise matching of the individual modules is crucial to obtain a good energy resolution. We have developped a calibration procedure for our total absorbing electromagnetic calorimeter which consists of 1022 lead fluoride (PbF_2) crystals. This procedure reconstructs the the single-module contributions to the events by solving a linear system of equations, involving the inversion of a 1022 x 1022-matrix. The system has shown its functionality at beam energies between 300 and 1500 MeV and represents a new and fast method to keep the calorimeter permanently in a well-calibrated state.
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