arXiv subjects

V. Chiarella

Publications and source records attributed to V. Chiarella.

23 records · Page 2Linked to original sources

arXiv2012

Measurement of the neutrino velocity with the OPERA detector in the CNGS beam

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km. The measurement is based on data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies. An arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (6.5 +/- 7.4(stat.)((+8.3)(-8.0)sys.))ns was measured corresponding to a relative difference of the muon neutrino velocity with respect to the speed of light (v-c)/c =(2.7 +/-3.1(stat.)((+3.4)(-3.3)(sys.))x10^(-6). The above result, obtained by comparing the time distributions of neutrino interactions and of protons hitting the CNGS target in 10.5 microseconds long extractions, was confirmed by a test performed at the end of 2011 using a short bunch beam allowing to measure the neutrino time of flight at the single interaction level.

hep-ex↗

arXiv2012

Determination of a time-shift in the OPERA set-up using high energy horizontal muons in the LVD and OPERA detectors

The purpose of this work is to report the measurement of a time-shift in the OPERA set-up in a totally independent way from Time Of Flight (TOF) measurements of CNGS neutrino events. The LVD and OPERA experiments are both installed in the same laboratory: LNGS. The relative position of the two detectors, separated by an average distance of ~ 160 m, allows the use of very high energy horizontal muons to cross-calibrate the timing systems of the two detectors, using a TOF technique which is totally independent from TOF of CNGS neutrino events. Indeed, the OPERA-LVD direction lies along the so-called "Teramo anomaly", a region in the Gran Sasso massif where LVD has established, many years ago, the existence of an anomaly in the mountain structure, which exhibits a low m. w. e. thickness for horizontal directions. The "abundant" high-energy horizontal muons (nearly 100 per year) going through LVD and OPERA exist because of this anomaly in the mountain orography. The total live time of the data in coincidence correspond to 1200 days from mid 2007 until March 2012. The time coincidence study of LVD and OPERA detectors is based on 306 cosmic horizontal muon events and shows the existence of a negative time shift in the OPERA set-up of the order of deltaT(AB) = - (73 \pm 9) ns when two calendar periods, A and B, are compared. This result shows a systematic effect in the OPERA timing system from August 2008 until December 2011. The size of the effect is comparable with the neutrino velocity excess recently measured by OPERA. It is probably interesting not to forget that with the MRPC technology developed by the ALICE Bologna group the TOF world record accuracy of 20 ps was reached. That technology can be implemented at LNGS for a high precision determination of TOF with the CNGS neutrino beams of an order of magnitude smaller than the value of the OPERA systematic effect.

hep-ex↗

arXiv2010

Search for neutral Higgs bosons decaying into four taus at LEP2

A search for the production and non-standard decay of a Higgs boson, h, into four taus through intermediate pseudoscalars, a, is conducted on 683 pb-1 of data collected by the ALEPH experiment at centre-of-mass energies from 183 to 209 GeV. No excess of events above background is observed, and exclusion limits are placed on the combined production cross section times branching ratio, ξ^2 = σ(e+e- --> Zh)/σ_{SM}(e+e- --> Zh) x B(h --> aa)x B(a --> τ^+τ^-)^2. For mh < 107 GeV/c2 and 4 < ma < 10 GeV/c2, ξ^2 > 1 is excluded at the 95% confidence level.

hep-ex↗

arXiv2010

Measurement of the atmospheric muon charge ratio with the OPERA detector

The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the atmospheric muon charge ratio in the TeV energy region. We analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime during the 2008 CNGS run. We computed separately the muon charge ratio for single and for multiple muon events in order to select different energy regions of the primary cosmic ray spectrum and to test the charge ratio dependence on the primary composition. The measured charge ratio values were corrected taking into account the charge-misidentification errors. Data have also been grouped in five bins of the "vertical surface energy". A fit to a simplified model of muon production in the atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.

hep-ex↗

arXiv2007

The ATLAS discovery potential for MSSM neutral Higgs bosons decaying to a mu+mu- pair in the mass range up to 130 GeV

Results are presented on the discovery potential for MSSM neutral Higgs bosons in the Mh-{max}scenario. The region of large tan beta, between 15 and 50, and mass between ~ 95 and 130 GeV is considered in the framework of the ATLAS experiment at the Large Hadron Collider (LHC), for a centre-of-mass energy = 14 TeV. This parameter region is not fully covered by the present data either from LEP or from Tevatron. The h/A bosons, supposed to be very close in mass in that region, are studied in the channel h/A -> mu+mu- accompanied by two b-jets. The study includes a method to control the most copious background, Zo -> mu+mu- accompanied by two b-jets. A possible contribution of the H boson to the signal is also considered.

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