Trigger and data acquisition: The bytes start and stop here Tschirhart, R.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2010, Letnik:
623, Številka:
1
Journal Article
Recenzirano
The modern trigger and data acquisition systems that instrument discovery experiments at the Large Hadron Collider (LHC) at CERN are very complex digital systems that select, reduce, and process ...enormous volumes of data in real-time to match the resources of state-of-the-art distributed computing available to researchers. Never before in particle physics have such powerful digital reconstruction and filtering systems been matched to a world-wide distributed system of computing of unprecedented scale. The goal of these massive aggregate computing systems is to extract as much physical information as possible from collision events at the LHC with well understood selection criteria and biases. Current strategies and future challenges in providing these aggregate real-time and offline computing systems are described.
Spin-Dependent WIMP Limits from a Bubble Chamber Behnke, E; Collar, J.I; Cooper, P.S ...
Science (American Association for the Advancement of Science),
02/2008, Letnik:
319, Številka:
5865
Journal Article
Recenzirano
Odprti dostop
Bubble chambers were the dominant technology used for particle detection in accelerator experiments for several decades, eventually falling into disuse with the advent of other techniques. We report ...here on a new application for these devices. We operated an ultraclean, room-temperature bubble chamber containing 1.5 kilograms of superheated CF₃I, a target maximally sensitive to spin-dependent and -independent weakly interacting massive particle (WIMP) couplings. An extreme intrinsic insensitivity to the backgrounds that commonly limit direct searches for dark matter was measured in this device under operating conditions leading to the detection of low-energy nuclear recoils like those expected from WIMPs. Improved limits on the spin-dependent WIMP-proton scattering cross section were extracted during our experiments, excluding this type of coupling as a possible explanation for a recent claim of particle dark-matter detection.
Abstract
This paper reports on the design and construction of a High Voltage Distribution System (HVDS) for a “Smart Switch” developed to provide high voltage (HV) to a series of stacked straw ...detector planes in the Mu2e Electron Tracking Detector (ETD). Each plane is composed of three 120 deg. Crescent-shaped panels, and each panel is composed of 96 straw tubes. The HVDS provides HV on-off, current monitoring, recording, and crowbar for over-current protection. The inter-communication system is based on TCP/IP. The HVDS supplies HV with long term stability, and accurately monitors the applied voltage and currents.
We present a new determination of the parity of the neutral pion via the double Dalitz decay pi0-->e+e-e+e-. Our sample, which consists of 30,511 candidate decays, was collected from KL-->pi0pi0pi0 ...decays in flight at the KTeV-E799 experiment at Fermi National Accelerator Laboratory. We confirm the negative pi0 parity and place a limit on scalar contributions to the pi0-->e+e-e+e- decay amplitude of less than 3.3% assuming CPT conservation. The pi0gamma*gamma* form factor is well described by a momentum-dependent model with a slope parameter fit to the final state phase-space distribution. Additionally, we have measured the branching ratio of this mode to be B(pi0-->e+e-e+e-)=(3.26+/-0.18)x10(-5).
Fermilab experiment E921, or Charged Kaons at the Main Injector (CKM), will measure the branching ratio of the ultrarare kaon decay: K/sup +//spl rarr//spl pi//sup +//spl nu//spl nu/. To do this, CKM ...will need to reject the far more copious decay K/sup +//spl rarr//spl pi//sup +//spl pi//sup 0//spl rarr//spl pi//sup +//spl gamma//spl gamma/ by a factor of more than 10 billion. Much of this rejection will come from the detection of either or both of the photons by our photon veto system. The main CKM photon veto system is based on 80-layer sandwiches of 1-mm Pb and 5-mm fast scintillator with wavelength shifting fibers inside a vacuum decay volume, read out with photomultiplier tubes outside the vacuum. We describe the design of the CKM photon veto system and the testing of a prototype in an electron beam at Jefferson National Laboratory, demonstrating an order of magnitude better performance than the required 3/spl times/10/sup -5/ inefficiency for a 1 GeV electromagnetic shower.
The observation of neutrons turning into antineutrons would constitute a discovery of fundamental importance for particle physics and cosmology. Observing the n–n̄ transition would show that baryon ...number (B) is violated by two units and that matter containing neutrons is unstable. It would provide a clue to how the matter in our universe might have evolved from the B=0 early universe. If seen at rates observable in foreseeable next-generation experiments, it might well help us understand the observed baryon asymmetry of the universe. A demonstration of the violation of B–L by 2 units would have a profound impact on our understanding of phenomena beyond the Standard Model of particle physics.
Slow neutrons have kinetic energies of a few meV. By exploiting new slow neutron sources and optics technology developed for materials research, an optimized search for oscillations using free neutrons from a slow neutron moderator could improve existing limits on the free oscillation probability by at least three orders of magnitude. Such an experiment would deliver a slow neutron beam through a magnetically-shielded vacuum chamber to a thin annihilation target surrounded by a low-background antineutron annihilation detector. Antineutron annihilation in a target downstream of a free neutron beam is such a spectacular experimental signature that an essentially background-free search is possible. An authentic positive signal can be extinguished by a very small change in the ambient magnetic field in such an experiment. It is also possible to improve the sensitivity of neutron oscillation searches in nuclei using large underground detectors built mainly to search for proton decay and detect neutrinos.
This paper summarizes the relevant theoretical developments, outlines some ideas to improve experimental searches for free neutron oscillations, and suggests avenues both for theoretical investigation and for future improvement in the experimental sensitivity.
Measurements of the decay KL-->e+ e- gamma Abouzaid, E; Arenton, M; Barker, A R ...
Physical review letters,
2007-Aug-03, 20070803, Letnik:
99, Številka:
5
Journal Article
Recenzirano
The E799-II (KTeV) experiment at Fermilab has collected 83 262 K(L)-->e+ e- gamma(gamma) events above a background of 79 events. We measure a decay width, normalized to the K(L)-->pi0pi0pi(D)0 ...(pi0-->gammagamma, pi0-->gammagamma, pi(D0-->e+ e- gamma(gamma)) decay width, of Gamma(K(L)-->e+e-gamma(gamma))/Gamma(K(L)-->pi0pi0pi(D)0)=(1.3302+/-0.0046(stat)+/-0.0102(syst)) x 10(-3). We also measure parameters of two K(L)gamma*gamma form factor models. In the Bergström-Massó-Singer parametrization, we find Calpha(K*)= -0.517 +/- 0.030(stat) +/- 0.022(syst). We separately fit for the first parameter of the D'Ambrosio-Isidori-Portolés model and find alpha(DIP)= -1.729 +/- 0.043(stat) +/- 0.028(syst).
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