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RIC h i lights

RIC h i lights. RICH2007 Highlights (Part III) Stefania Ricciardi RAL, 28 November 2007. Piazza Unita` d’Italia. Caffe` degli Specchi (Mirrors) One of Trieste “institutions” appreciated by Kafka, Joyce and British Royal Navy which chose it as General Quarter at the end of second World War

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RIC h i lights

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  1. RIChilights RICH2007 Highlights (Part III) Stefania Ricciardi RAL, 28 November 2007

  2. Piazza Unita` d’Italia Caffe` degli Specchi (Mirrors) One of Trieste “institutions” appreciated by Kafka, Joyce and British Royal Navy which chose it as General Quarter at the end of second World War Named after large mirrors on the wall used to reflect inside the light from the sunset on the sea

  3. Right ingredients for a successful RICH conference! Piazza Unita` d’Italia Mirrors Water

  4. RICH2007 Sessions • Cherenkov light imaging in particle and nuclear physics experiments • Cherenkov detectors in astroparticle physics • Novel Cherenkov Imaging Techniques • Photon detection for Cherenkov counters • Technological aspects of Cherenkov detectors • Pattern recognition and data analysis • Exotic applications of Cherenkov radiation

  5. RICH in AstroParticle Physics Cherenkov detectors are fundamental in many APP sectors. Discussed @ RICH2007 • Ground-based gamma-ray astonomy • @ RICH2007: MAGIC • Cherenkov Imaging detectors for ion identification in CR (satellite and balloon-born experiments) • Flying spectrometers • @ RICH2007: CREAM • High-energy n telescopes • high mass targets (≈ 109 t)  use large volumes of transparent media available in nature • @ RICH2007: Antares, Nemo, KM3Net (Ref to Recent seminar at RAL by Greg Hallewell)

  6. The experimental challenge in high energy astrophysics E.Lorenz INITIAL PARAMETERS NOT UNDER CONTROL AS IN HEP ENERGY , TIME, (PATRICLE TYPE), (DIRECTION) FLUXES ARE VERY LOW -> NEEDS ULTRA-LARGE DETECTOR VOLUMES WATER – ICE – AIR natural media act as target and radiators (transparent to light)  allow the construction of massive Cherenkov instruments with excellent performance for neutrino and astroparticle physics NEARLY ALL EXPERIMENTS IN APP RELY ON PHOTON DETECTION Need for large-active-area single-photon AstroParticle Physics is now a driving force for new photon detectors.

  7. GROUND-BASED g ASTRONOMY Started in 1989 by discovery of gs from the CRAB Nearly all discoveries made by Cherenkov light detectors (> 95%): Imaging Air Cherenkov Telescopes 44 SOURCES (13 As) (NOW(FALL07) 70 SOURCES 2006) NOT ALL SOURCES IN INNER GALACTIC PLANE SHOWN

  8. The IACT technique Physics of the atmospheric showers: • Cosmic rays (protons, heavier Z, electrons, photons) hit the upper atmosphere • Interactions create cascade of billions of particles: • Electromagnetic shower (e+,e-,) • Hadronic shower (, , e+,e-,) • Charged particles in turn emit Cherenkov light: • Blueish flash • ~2ns duration • ~1º aperture • Cherenkov cone reaches the ground • Circle of ~120m radius

  9. IACT g-image • Image is ellipsoid pointing to centre for gammas (axis aligned with g-source) • Randomly distributed for hadrons • Study of the image gives information on primary particle Sensitivity to single photons and the best possible time resolution are important, because the signal is weak, and the discrimination against non-electromagnetic showers is helped by determining precise arrival times. Signal:100 photons/m2 at 1 TeV Background: 2-5 1012 photons/(s m2 sr) High quality photomultipliers are used as photon detectors.

  10. THE NEW GENERATION OF HIGH SENSITIVITY CHERENKOV TELESCOPES MAGIC(Germany, Italy & Spain) 20031 telescope 17 meters Ø VERITAS(USA & England)20074 telescopes10 meters Ø Whiple obs. Base camp Arizona Roque delos Muchachos, Canary Islands CANGAROO III(Australia & Japan) 20044 telescopes 10 meters Ø Komas land, Namibia HESS(Germany & France) 20024 telescopes 12 meters Ø Woomera, Australia

  11. The MAGIC Telescope M.Doro • Collaboration of 22 institutes (mostly European) ~150 physicists • Installation completed 2003 • Clone (Magic II) under construction • Inauguration 2008 • Stereoscopic MAGIC I + II will have increased performance:angular resolution • energy resolution, flux sensitivity Focal plane camera with 580 PMTs

  12. M.Doro MAGIC Reflector and mirrors: • World largest dish diameter 17m • All aluminium mirrors with sandwich structure and diamond-milled surface Mirror requirements AlMgSi0.5 plate Hexcell Al Box

  13. MAGIC Summary M.Doro • MAGIC II mirrors production is already on the production-line • Technique gave excellent results in term of light concentration • Insulating problems seem solved • Price is decreased wrt to MAGIC I, nevertheless is still main drawback: 2.8k€/m2 can be a problem for third generation IACTs • Scale production can decrease costs or find other techniques (glass)

  14. NEXT AIR CHERENKOV TELESCOPE PROJECTS Aim for higher sensitivity (factor 10 increase), lower threshold (<50 GeV) European initiative: CTA (Cherenkov telescope array) US Project: AGIS Both in the 100-150 M€ price range, 50-100 telescopes CTA

  15. Y.Sallaz-Damaz

  16. CREAM

  17. CHERCAM a flying Cherenkov.. Launch expected Dec 2007 Optimised for charge measurement (Nph Z2 sin2q, resolution 0.2 charge units) Has to operate a low temperature/low pressure (-10C, 5mb)

  18. PID and Pattern recognition can be a complex business – many challenges.. SuperK (multiple) rings 2 electron candidates: 2 muon candidates: The largest Cherenkov in use at an accelerator-based experiment 50ktonnes water viewed by 13,000 20” PMTs

  19. In Search of the Rings (not the speaker) Approaches to Cherenkov Ring Finding and Reconstruction in HEP Guy Wilkinson, Oxford University RICH 2007, Trieste, October 2007

  20. Challenges of RICH pattern recognition in PP LHCb: RICH 1 (revolved !) Complicated environment ! Lesson 1: main source of background is other rings.

  21. Ring without associated track Split (or partial) rings Sparsely populated rings Challenges in RICH Pattern Recognition LHCb: RICH 1 (revolved !)

  22. Likelihood algorithms Likelihood approach is most common method of pattern-recognition + PID (note - it performs both steps!) for experiments where tracking info is available. eg. LHCb, BaBar, CLEO-c, Hermes, HERA-B, DELPHI, SLD… For a given set of photons which are candidates to be associated with the track, formulate a likelihood for each particle hypothesis (e, μ, π, K, p). Eg. for CLEO-c: 1 < p < 1.5 GeV/c background distribution expect a certain number of photons, at a certain angle, with a certain resolution there may be several paths by which photon has reached detector Ratio of likelihoods, or difference of log-likelihoods then gives a statistically meaningful quantity that can be cut on to distinguish between hypotheses.

  23. Global Likelihood Very often it is advantageous to calculate a single (log) likelihood for all event, being the (sum) product of the likelihoods for all of the tracks in all radiators. • In high-multiplicity environments, the background to each signal ring • is… other signal rings! Only way to get an unbiased estimate for each track is to consider entire event simultaneously. • In experiments with >1 radiator or >1 counters (eg. LHCb 3 radiators • in 2 counters, SLD liquid and gas, HERMES aerogel and gas…) this • is a convenient way to make best use of all information. Likelihood maximised by flipping each track hypothesis in turn until convergence is attained.

  24. Performance of likelihood algorithms Kaon identification efficiency, and  misid efficiency: LHCb: K (or p) preferred hypothesis BaBar: LK > L

  25. Detector space HT Space r or θc Hough Transform yc xc Hough transforms Hough Transform: common technique in both tracking & ring finding. Attractive features - unaffected by topological gaps in curves, split images, and is rather robust against noise. Each point gives surface in HT space. Intersection of surfaces gives ring parameters. Find by peak hunting in suitably binned histogram. Usual practice: look for centre OR radius, ie. reduce to 2-d or 1-d problem. Used by several experiements in high-density environment: Alice, CERES

  26. 11,146 PMTs 36.2 m 33.8 m HT Applications of Hough trasforms in n physics: SuperK No tracking info available in SuperK: standalone ring-finding essential Firstly find event vertex position based on spread of hit PMT times Find vertex to resolution of ~ 30 cm Initial direction indicator also available. Then perform HT: draw saturated (42 0) circles around hit tubes to look for ring centres and hence directions. Iterate, to look for multiple ring candidates

  27. Conclusions on reconstruction and ID techniques Likelihood algorithms and Hough Transforms have proven record of making sense of even the most intimidating environments. In general these make significant use of tracking information. Other approaches exist, but have not yet achieved performance to displace baseline methods. Will be interesting to see how methods developed on MC for high multiplicity experiments (eg. LHCb, ALICE) cope with real data! COMPASS STAR BABAR DIRC

  28. “Exotic applications of Cherenkov radiation” Ice Salt domes Lunar regolith This is NOTexotic nowadays!

  29. Radio-Cherenkov detectors • Active experiments: • RICE (since 1999) • Anita Physics: UHE n Detection of EeV neutrinos (i.e. GZK neutrinos produced in interaction of UHE protons with CMB) p +gCMB (→D* → np+) → n e+nenmnm Flux is extremely low: 10 GZK n/km2/y 300 Km interaction length for En=1018 eV Need >>102 km3 volumes Salsa (Anita Collaboration)

  30. The Askaryan effect

  31. Anita

  32. Conclusion The three of us did appreciate the conference and the setting! A.P. S.E.

  33. Many thanks to the Organisers! RICH 2007 Stazione Marittima, Trieste, Italy October 2007

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