Скачать презентацию Accelerator searches for oscillations Roumen Tzenov CERN and Скачать презентацию Accelerator searches for oscillations Roumen Tzenov CERN and

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Accelerator searches for oscillations Roumen Tzenov CERN and University of Sofia Ioannina, 20 -23 Accelerator searches for oscillations Roumen Tzenov CERN and University of Sofia Ioannina, 20 -23 April 2000

Legend • Introduction to neutrino oscillations • Short baseline accelerator searches for – CHORUS Legend • Introduction to neutrino oscillations • Short baseline accelerator searches for – CHORUS – NOMAD • Future long baseline accelerator searches

Neutrino mixing Associate neutrino flavour with the charged lepton flavour as seen in charged-current Neutrino mixing Associate neutrino flavour with the charged lepton flavour as seen in charged-current interactions: For massive neutrinos: flavour eigenstate need not be a mass eigenstate but can be a coherent superposition: Mixing matrix U is unitary The propagation of different mass eigenstates leads to flavour oscillation in vacuum: Simplification for 2 mixing flavours with mixing angle q (phase d): Interactions are now nondiagonal with the mass eigenstates!

Neutrino oscillations The probability that a neutrino oscillates (changes flavour): With definition: To have Neutrino oscillations The probability that a neutrino oscillates (changes flavour): With definition: To have a large effect: Maximum at 1/4 oscillation length

Dm 2 (e. V 2) Two parametric oscillation plot Cosmologically relevant Solar n + Dm 2 (e. V 2) Two parametric oscillation plot Cosmologically relevant Solar n + seesaw + DM ? 100 10 1 10 -2 10 -3 10 -4 10 -5 10 -6 10 -7 10 -8 10 -9 10 -10 10 -11 10 -12 LSND Atmospheric n Kamiokande Super. Kamiokande Solar n (MSW) CHOR US and NOMA D Solar n (vacuum oscillation) 10 -5 10 -4 10 -3 sin 2 10 -2 2 Q 10 -1 1. e e e

The Collaboration Belgium (Brussels, Louvain-la-Neuve), CERN, Germany (Berlin, Münster), Israel (Haifa), Italy (Bari, Cagliari, The Collaboration Belgium (Brussels, Louvain-la-Neuve), CERN, Germany (Berlin, Münster), Israel (Haifa), Italy (Bari, Cagliari, Ferrara, Naples, Rome, Salerno), Japan (Toho, Kinki, Aichi, Kobe, Nagoya, Osaka, Utsunomiya) , Korea (Gyeongsang), The Netherlands (Amsterdam), Russia (Moscow), Turkey (Adana, Ankara, Istanbul)

CHORUS Main objective • nt appearance in the SPS WBB n beam via oscillation CHORUS Main objective • nt appearance in the SPS WBB n beam via oscillation • P(n ® nt ) down to 1 • 10 -4 for m 2 ~10 e. V 2 • nt direct detection in 770 kg nuclear emulsion target Tag: visible 1 - and 3 - prongs decay of primary -lepton (decay path ~1. 5 mm) - h- n o e- e BR 18 % + - - n o 50 % 18 % 14 % “Kink”

CERN West Area Neutrino Facility 450 Ge. V SPS Beryllium protons target horn reflector CERN West Area Neutrino Facility 450 Ge. V SPS Beryllium protons target horn reflector vacuum tunnel earth/iron shielding ~0. 6 km; L(rms)/L~0. 2 124 m • WBB, = 26. 6 Ge. V 290 m • ~5 • 10 19 protons on target • ~840 K CC in CHORUS CC / CC ~ 3. 10 -6 • (~0. 1 background event) 408 m CHORUS NOMAD

WANF West Area Neutrino Facility The “horn” WANF West Area Neutrino Facility The “horn”

SPS and WANF (n ) neutrino beam SPS and WANF (n ) neutrino beam

CHORUS detector Nucl. Instr. Meth A 401 (1997) 7 - T=5° Calorimeter h 770 CHORUS detector Nucl. Instr. Meth A 401 (1997) 7 - T=5° Calorimeter h 770 kg emulsion target and scintillating fibre tracker Muon spectrometer Air core spectrometer and emulsion tracker Veto plane

Scintillating fibre trackers Nucl. Instr. Meth A 412 (1998) 19 ~ 2 mrad, xy~150 Scintillating fibre trackers Nucl. Instr. Meth A 412 (1998) 19 ~ 2 mrad, xy~150 mm

External electronic detectors: • sign and momentum of pions • Hadronic and e-m shower External electronic detectors: • sign and momentum of pions • Hadronic and e-m shower energy and direction • Muon momentum and id Event pre-selection and post -scanning analysis P(h±)<20 Ge. V/c p/p ~25% 3

Neutrino data-taking collection efficiency 1994 -1997 N. B. Longest/Largest emulsion exposure ever done Neutrino data-taking collection efficiency 1994 -1997 N. B. Longest/Largest emulsion exposure ever done

e tanq Predictions and Scanback e tanq Predictions and Scanback

Nuclear emulsion yesterday u 1947, first nuclear emulsions. Lattes et al. , Brown et Nuclear emulsion yesterday u 1947, first nuclear emulsions. Lattes et al. , Brown et al. : Discovery of e

CHORUS emulsion plate Target = 4 stacks (1. 4 m 2) 1 stack = CHORUS emulsion plate Target = 4 stacks (1. 4 m 2) 1 stack = 36 plates MIP : 30 40 grains / 100 m 1/4 plate 100 m emulsion 350 mkm base 90 mkm – Grain size ~ 0. 3 mm 80 m – Angular resolution 1. 5 mrad

CHORUS automatic microscopes CCD and XYZ stage New Track Selector Host CPU Network data CHORUS automatic microscopes CCD and XYZ stage New Track Selector Host CPU Network data storage

CHORUS automatic microscopes Megapixel CCD and XYZ stage DSPs High Performance optics 1 m CHORUS automatic microscopes Megapixel CCD and XYZ stage DSPs High Performance optics 1 m Processing Cluster

Inside a “vertex plate” n beam -54 mm -36 mm View size: 120 x Inside a “vertex plate” n beam -54 mm -36 mm View size: 120 x 150 m 2 Focal depth : ~3 m Red frame: ~30 x 40 m 2 -21 mm 0 mm

Decay search Decay search

t- kink detection (parent search) Principle: Principle Parent track ( ) can be detected t- kink detection (parent search) Principle: Principle Parent track ( ) can be detected by wider view and general angle scanning at the vertex plate Offline selection small impact parameter between parent and daughter n kink point is in the vertex plate n scan-back track Impact parameter or h general scanning area

Off-line video-image analysis CHORUS Emulsion Display Off-line video-image analysis CHORUS Emulsion Display

Manual scanning on special events: Diffractive D*s production, double leptonic decay Phys. Lett. B Manual scanning on special events: Diffractive D*s production, double leptonic decay Phys. Lett. B 435(1998) 458 -464.

Status of Phase I scanning * 0 decay search not finished yet (1996 -1997), Status of Phase I scanning * 0 decay search not finished yet (1996 -1997), not included in current results

t Det efficiency: Ratio of Acceptances S=Nt if P t=1 A=detector acceptance N 1 t Det efficiency: Ratio of Acceptances S=Nt if P t=1 A=detector acceptance N 1 =normalization h=Kink finding efficiency In the same way, it is applied to the 0 sample Located Vertexes

Background • 1 sample ( - -) – charm production from antineutrino CC (with Background • 1 sample ( - -) – charm production from antineutrino CC (with primary lepton (e+ or +) unidentified ~10 -6 / - nt contamination of the beam N 1 ~10 -7 / N 1 • 0 sample ( - h-) – charm production from antineutrino CC ~2 • 10 -6 / N 1 – 1 -prong nuclear interaction without visible recoil or nuclear break-up (White kinks) ~2 • 10 -5 / N 1

Current Result • No n candidates CHORUS current limit found sin 2 2 < Current Result • No n candidates CHORUS current limit found sin 2 2 < 8 • S = 6003 ± 17% (syst) • P < 2. 38 / 6003 = (@ 90% C. L. ) m 2/e. V 2 • n n CC (expected) = P • S, 4 • 10 -4 Includes also 17% systematic error (NIM A 320 (1993) 331) sin 2 2 • 10 4

Outlook: • Phase I scanning: Going to finish this year Expected gain in sensitivity: Outlook: • Phase I scanning: Going to finish this year Expected gain in sensitivity: • ~1. 2 from 1 (short decays, statistics) • ~1. 2 from 0 (3 prongs, 0 96+97) • Phase II scanning and analysis: years 2000 -2001 • New generation of automatic systems • Upgraded predictions • 3 prongs dedicated search • e ? (electron id by MS in emulsion) • Full vertex analysis (NETSCAN, General tracking) charm physics: |Vcd|2, cc, D+/D 0 P < 1. 0 • 10 -4 (in absence of -candidates)

What to dofurther with accelerator beams? What to dofurther with accelerator beams?

Long baseline experiments Long baseline experiments

Long base line beams compared to WANF Long base line beams compared to WANF

MINOS detector MINOS detector

ICANOE detector ICANOE detector

OPERA detector 200 ton iron/emulsion sandwiches + muon identificator OPERA detector 200 ton iron/emulsion sandwiches + muon identificator

OPERA module OPERA module

Long baseline experiments’ claims. . . Long baseline experiments’ claims. . .

Conclusion u Current short baseline accelerator searches for oscillations have almost done their job; Conclusion u Current short baseline accelerator searches for oscillations have almost done their job; u No oscillations seen (so far) for large m 2 and small mixing angles; u Atmospheric neutrino data suggest, on the opposite, small mass difference and large mixing angle; u Several long baseline accelerator experiments are on the start scratch to clarify the issue. . .