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The OPERA experiment

The OPERA experiment. CERN. 730 km. LNGS. 1400 m. Neutrinos. OPERA. Designed in 2000 to search for Neutrino Oscillations via the detection of tau neutrinos First neutrinos from CERN detected in 2006. CERN. 730 km. LNGS. Neutrino velocity measurement Neutrinos production time (CERN)

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The OPERA experiment

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  1. The OPERA experiment CERN 730 km LNGS 1400 m Neutrinos OPERA Designed in 2000 to search for Neutrino Oscillations via the detection of tau neutrinos First neutrinos from CERN detected in 2006

  2. CERN 730 km LNGS • Neutrino velocity measurement • Neutrinos production time (CERN) • Neutrinos interaction time (OPERA detector) • Accurate determination of the distance • (Geodesy) • Dedicated upgrade in 2008 • Largest application of metrology techniques in HEP • 2009-2011 measurement with standard CNGS beam  Blind analysis: • “box” opened after assessment of delays(previously fixed to arbitrary values): nm Time Space • High neutrino energy - high statistics ~15000 events • Precise measurement of neutrino time distribution at CERN through proton waveforms • Sophisticated timing system: ~1 ns CNGS-OPERA synchronization • Calibrations techniques of CNGS and OPERA timing chains: ~ 1 ns level • Measurement of baseline by global geodesy: 20 cm accuracy over 730 km • (longest neutrino baseline actually available) • Result: ~10 ns overall accuracy on TOF with similar stat. and sys. errors 2

  3. y x z Summary of the principle for the TOF measurement Measure dt =TOFc - TOFn 3 3

  4. Protons timing 2 km Beam Current Transformer Recorded waveform of a pulse of protons 10.5 ms

  5. LNGS ESAT 2000 GPS PolaRx2e GPS PolaRx2e Atomic clock Cs 4000 Atomic clock Cs 4000 CERN CERN

  6. Geodesy at LNGS Dedicated measurements at LNGS: July-Sept. 2010 2 new GPS benchmarks on each side of the 10 km highway tunnel  ported underground to OPERA CERN and LNGS measurements combined in ETRF2000 GPS Distance CERN BCT-OPERA GPS (731278.0 ± 0.2) m Monitor continental drift and important geological events (e.g. 2009 earthquake) 6

  7. Neutrino data vs protons: after delay determination (2009-2011) ~15000 neutrinos Dots: neutrino events Red line: protons BLIND: dt = TOFc-TOFn = (1043.4 ± 7.8) ns • Blind cross-checks: • Accuracy of analysis method • Stability in the 3 years • Day/night • Warm/cold • External interactions • Running conditions

  8. OPENING OF THE BOX March 2011 very surprising result neutrinos anticipate light by 60 ns (20 m over 730 km)  6 months of verifications campaign: synchronization, geodesy, detector, accelerator, each aspect of the measurement cross-checked with at least two independent techniques UNBLIND: dt = (57.8 ± 7.8 (stat.) -5.9 +8.3 (sys.)) ns September 2011, anomaly still alive  involve the rest of the physics community in order to help in understanding its nature, speed up the investigation and try to replicate the effect under different conditions Seminar at CERN (23/9/2011) and simultaneous publication of all the elements of the measurement: • The OPERA detector at LNGS in the CERN CNGS muon neutrino beam has allowed the most sensitive terrestrial measurement of the neutrino velocity over a baseline of about 730 km. • Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to identify any still unknown systematic effect. • We do not attempt any theoretical or phenomenological interpretation of the results. 8

  9. Measurement with a dedicated beam (November 2011) A beam of very short pulses (3ns) separated by long empty intervals 10.5 ms 1 ms Time of flight individually measured for 20 neutrinos in one week dt = TOFc-TOFn= (62.1 ± 3.7 (stat.)) ns

  10. Further investigations since November 2011 • Discussion of a new bunched beam campaign (indicative date May 2012) with improved beam performance (100 ns bunch spacing, a factor 3 more intensity). More accurate study for possible energy dependence and measurement with anti-neutrinos. Other LNGS experiments (ICARUS, BOREXINO, LVD) involved. • Development of a new time-transfer system at CERN and LNGS based on the White-Rabbit protocol (self-calibrating continuous delay measurement) • Developments for DAQ upgrade for May 2012 run by including TDCs at the level of the Master clock (±25 ns jitter) and FE sensors (± 5 ns jitter) • Additional checks on the Geodesy at CERN on the underground transport of external GPS measurements • Additional checks on GPS timing with a two-way satellite transfer measurement and possible time-transfer via optical fibers • Additional measurements at LNGS (winter 2011 shutdown): •  identified two unknown sources of bias on TOF, going in opposite directions • (22 Feb. 2012) 10

  11. New direct measurement campaign of 10-24 May 2012: • 1) Improvements in OPERA timing • New OPERA master clock installed • Better timing  time resolution twice better • Better local oscillator, small frequency offset 5ns/s (124 ns/s old oscillator) • Continuous monitoring of the local oscillator frequency and fiber transmission delay using the “White Rabbit” system • d) Better stability of Master Clock delay response with respect to light input from the fiber • 2) Improvements in the CNGS beam timing structure • November 2011: 4 short bunches separated by 524 ns • May 2012: 64 short bunches separated by 100 ns • 3) Improvements in timing equipment systematics • Double GPS system • White Rabbit monitoring of all time transfer delays at CERN and LNGS • Beam Current Transformer (BCT) calibration redone. Before: BCT systematic error of 5 ns (the largest sys. error affecting the measurement). Now: only 1 ns ! 106 events collected 59 events selected by the analysis cuts (factor 3 better statistics, factor 2 better resolution, redundancy) 11

  12. The CNGS neutrino beam • 40000 billions of protons accelerated to 400 GeV energy • Every 6 s  two pulses of 10.5 ms (50 ms gap) • Almost pure nm beam (average energy = 17 GeV)

  13. Neutrinos seen by the OPERA detector nmCC m from external interaction NC “EXTERNAL” EVENTS (interactions in the rock) “INTERNAL” EVENTS 13

  14. The GPS “a marvelous tool” Standard GPS receiver: finds x, y, z, t of the observer with ≥ 4 satellite observations, by solving 4 equations in 4 unknowns If x, y, z are fixed  one satellite enough to measure t Common-view mode: same satellite seen at the two sites Special GPS receiver + atomic clock  Time-transfer (~1 ns accuracy ) Used in the definition of TAI (International Atomic Time) 14

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