The Austroalpine Sesia-Lanzo inlier and upper Austroalpine Dent Blanche, Mt. Mary and Pillonet outliers occur on top of the western-Alpine orogenic wedge and, as a whole, override the structurally ...composite ophiolitic Piemonte zone. Instead, the Mt. Emilius, Glacier-Rafray, Etirol-Levaz and other lower Austroalpine eclogitic outliers are inserted within the Piemonte zone, between its upper (Combin) and lower (Zermatt-Saas) tectonic elements, or within the latter. Rb-Sr dating on phengitic micas show that the eclogitic imprint in the lower Austroalpine outliers, conventionally regarded as Late Cretaceous by comparison with the Sesia-Lanzo inlier, is of Eocene age (49-40 Ma), like the underlying Zermatt-Saas ophiolite (45-42 Ma) between the Aosta valley and Gran Paradiso massif. super(40)Ar- super(39)Ar plateau ages on the same mica concentrates of the ophiolitic Zermatt-Saas nappe (46-43 Ma) are consistent with Rb-Sr dating, whereas that on the Austroalpine Glacier-Rafray klippe (92 Ma) is influenced by argon excess. The lower Austroalpine outliers underwent the subduction metamorphism concurrently with the Zermatt-Saas nappe, 20-25 Ma later than the eclogitic Sesia-Lanzo inlier and blueschist Pillonet klippe. The temporal gap and present intra-ophiolitic position mean that the lower Austroalpine outliers were probably derived from an intraoceanic extensional allochthon (Mt. Emilius domain) stranded inside the Piemonte-Ligurian ocean far from the Dent Blanche-Sesia domain and Adriatic margin.
Triggering on B-Jets at CDF II Amerio, S.; Casarsa, M.; Cortiana, G. ...
IEEE transactions on nuclear science,
06/2009, Letnik:
56, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In this paper we present a trigger algorithm able to select online events enriched of b-jets. This feature is of central interest in order to extend the physics reach for standard model and minimal ...super symmetric model Higgs decaying into a pair of b -quarks. The algorithm fully exploits the recently upgraded CDFII tracking system and Level 2 CALorimeter cluster finder. These upgrades are necessary to cope with Tevatron increasing luminosity and provide new and refined trigger primitives that are the key elements of our algorithm together with the already existing silicon vertex trigger. A b -hadron can travel some millimeters before decaying and the trigger algorithm exploits this characteristic by searching for tracks displaced with respect to the primary vertex and matched to energetic jets of particles. We discuss the study and the optimization of the algorithm, its technical implementation as well as its performance. The new trigger provides an efficient selection for Higgs decaying into a pair of b -quarks and runs up to high luminosity with an acceptable occupancy of the available bandwidth.
Level-2 Calorimeter Trigger Upgrade at CDF Bhatti, A.; Canepa, A.; Casarsa, M. ...
IEEE transactions on nuclear science,
06/2009, Letnik:
56, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The CDF Run II level 2 calorimeter trigger is implemented in hardware and is based on a simple algorithm that was used in Run I. This system has worked well for Run II at low luminosity. As the ...Tevatron instantaneous luminosity increases, the limitation due to this simple algorithm starts to become clear. As a result, some of the most important jet and MET (missing ET) related triggers have large growth terms in cross section at higher luminosity. In this paper, we present an upgrade of the L2CAL system which makes the full calorimeter trigger tower information directly available to the level 2 decision CPU. This upgrade is based on the Pulsar, a general purpose VME board developed at CDF and already used for upgrading both the level 2 global decision crate and the level 2 silicon vertex tracking. The upgrade system allows more sophisticated algorithms to be implemented in software and both level 2 jets and MET can be made nearly equivalent to offline quality, thus significantly improving the performance and flexibility of the jet and MET related triggers. This is a natural expansion of the already-upgraded level 2 trigger system, and is a big step forward to improve the CDF triggering capability at level 2. This paper describes the design, the hardware and software implementation and the performance of the upgrade system.
Evidence is reported for a narrow structure near the $J/\psi\phi$ threshold in exclusive $B^+\to J/\psi\phi K^+$ decays produced in $\bar{p} p $ collisions at $\sqrt{s}=1.96 \TeV$. A signal of ...$14\pm5$ events, with statistical significance in excess of 3.8 standard deviations, is observed in a data sample corresponding to an integrated luminosity of $2.7 \ifb$, collected by the CDF II detector. The mass and natural width of the structure are measured to be $4143.0\pm2.9(\mathrm{stat})\pm1.2(\mathrm{syst}) \MeVcc$ and $11.7^{+8.3}_{-5.0}(\mathrm{stat})\pm3.7(\mathrm{syst}) \MeVcc$.
We report the observation of B{sub s}{sup 0}-B{sub s}{sup 0} oscillations from a time-dependent measurement of the B{sub s}{sup 0}-B{sub s}{sup 0} oscillation frequency {delta}m{sub s}. Using a data ...sample of 1 fb{sup -1} of pp collisions at {radical}(s)=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic B{sub s} decays, 3100 partially reconstructed hadronic B{sub s} decays, and 61 500 partially reconstructed semileptonic B{sub s} decays. We measure the probability as a function of proper decay time that the B{sub s} decays with the same, or opposite, flavor as the flavor at production, and we find a signal for B{sub s}{sup 0}-B{sub s}{sup 0} oscillations. The probability that random fluctuations could produce a comparable signal is 8x10{sup -8}, which exceeds 5{sigma} significance. We measure {delta}m{sub s}=17.77{+-}0.10(stat){+-}0.07(syst) ps{sup -1} and extract vertical bar V{sub td}/V{sub ts} vertical bar =0.2060{+-}0.0007({delta}m{sub s}){sub -0.0060}{sup +0.0081}({delta}m{sub d}+theor)
We report the observation and measurement of the mass of the bottom, strange baryon Xi-_b through the decay chain Xi-_b --> J/psi Xi-, where J/psi --> mu+ mu-, Xi- --> Lambda pi+-, and Lambda --> p ...pi+-, and Lambda --> p pi+-. Evidence for observation is based on a signal whose probability of arising from the estimated background is 6.6 x 10-15, or 7.7 Gaussian standard deviations. The Xi-_b mass is measured to be 5792.9 +/- 2.5 (stat.) +/-1.7 (syst.) MeV/c2.
ATLAS is a multi purpose detector built to study proton-proton collisions, at center of mass energies up to 14 TeV, as provided by the Large Hadron Collider at CERN. ATLAS is equipped with an inner ...charged particle tracking system composed of silicon and drift tube based detectors. The required precision for the alignment of the most sensitive coordinates of the silicon sensors is at the level of few microns, the limit being derived by the requirement that module misalignments should not worsen the resolution of the track parameter measurements by more than 20%. In these proceedings, the outline of the alignment approaches and results obtained using real data from cosmic rays and large scale computing simulation of physics samples, are presented. Cosmic ray data serves to derive an early set of alignment constants for the ATLAS ID before the LHC start up. The impact of the alignment on physics measurements will be discussed.
We have searched for exclusive 2-photon production in proton-antiproton collisions at sqrt{s} = 1.96 TeV, using 532/pb of integrated luminosity taken by the Run II Collider Detector at Fermilab. The ...event signature requires two electromagnetic showers, each with transverse energy E_T > 5 GeV and pseudorapidity |eta|<1.0, with no other particles detected in the event. Three candidate events are observed. We discuss the consistency of the three events with gamma-gamma, pi0-pi0, or eta-eta production. The probability that other processes fluctuate to 3 events or more is 1.7x10^-4. An upper limit on the cross section of p+pbar --> p+gamma-gamma+pbar is set at 410 fb with 95% confidence level.
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