Futuri progetti agli acceleratori

Transcription

1 Futuri progetti agli acceleratori IFAE Lecce 24/4/2003 Prospettive sulle oscillazioni di neutrino Fasci convenzionali di neutrino Nuovi fasci di neutrino: beta beams, superbeams, neutrino factories R&D verso una neutrino factory Conclusioni M. Bonesini Sezione INFN Milano 1

2 1. 3-Generation Neutrino Oscillation Formalism For 3-generations: ν e, ν µ, and ν τ (and maybe even more... the sterile neutrino ν s s ) νe ν µ ντ = s 12 s s c c c c c c s iδ 13e s s c 12 c c s 23 s 12 s c 12 s 13 s c s s e 13 iδ e iδ s 13 s c e iδ c c ν1 ν 2 ν 3 CKM-like Mixing Matrix for Leptons Present limit from CHOOZ : sin 2 2θ 13 < 0.1. Both solar and atmospheric results are compatible with θ 13 =0. Solar + atmospheric neutrinos favour a near bi-maximal mixing matrix (very different from CKM matrix). Θ 13 drives ν µ > ν e subleading transitions -> the necessary milestone for CP violation search,... M Bonesini - INFN Milano 2

3 A Crystal Ball View Near-term long-baseline experiments focused on dominant ν µ ν τ channel Expect ~few percent measurements Possible direct observation of ν τ appearance Limited sensitivity to sin 2 2θ 13 Mini-BOONE will test LSND Precision mixing measurements imperative if confirmed M Bonesini - INFN Milano 3

4 Next Generation Goals Precision measurement of dominant oscillation ν µ ν τ channel Determine sign of m 23 2 Sensitivity to sub-dominant ν µ ν e channel at 1 level Sensitivity to δ CP Probably a phase 2 goal, after θ 13 M Bonesini - INFN Milano 4

5 NOW K2K-II νµ disappearance HARP KamLand MiniBooNE Roadmap JHFν Θ13 down to 1 o MICE νf R&D CNGS NuMI? Off-Axis Θ13 m 2 12,θ 12 at 2% τ appearance NC/CC LSND? 2015? νfactory CP violation From L. Ludovici with some editing 2020 M Bonesini - INFN Milano 5

6 2. Conventional ν µ beams (from π decay) Primary protons hit target π + produced at 1 to 100 milli-radian angles magnetic horn to focus π + π + decay to µ + ν in long decay pipe left-over hadrons shower in hadron absorber rock shield ranges out µ + ν beam travels through earth to experiment p Target π + Decay Pipe Hadron Absorb. µ + Rock ν Exp. Horns M Bonesini - INFN Milano 6

7 ν beams: conventional and nufact beams Wanf Nufact Problem in conventional beams: a lot of minority components Following the studies for the muon collider, accelerated muons are ALSO an intense source of high energy neutrinos (µ + > e + ν e ν µ, µ >eν e ν µ ). Crucial features high intensity (x 100 conventional beams known beam composition (50% ν µ 50% ν e ) Possibility to have an intense ν e beam Essential detector capabilities: detect muons and determine their sign 7

8 Big problem in conventional ν beams experiments: beam understanding Use standard MC simulation : Geant, Fluka, Mars to full simulate target production +beamline (SLOW) Use dedicated parametrizations for secondary production in target ( Sanford-Wang, Malensek, BMPT... based on available data (Na56/SPY,...) + simulation of beamline (FAST) Minority components -> needs better knowledge of secondary production in target. More data needed on hadroproduction M Bonesini - INFN Milano 8

9 3. Neutrino Factories The ultimate tool for probing neutrino oscillation, based on muon decays (NOT π DECAY!!!) Enormous luminosity Exceptional purity Perfect knowledge of spectrum Flavor of initial neutrino tagged by charge Caveats: Technical challenges to muon acceleration Cost Proton drivers Targetry Particle production measurements RF manipulation Cooling Muon acceleration M Bonesini - INFN Milano 9

10 10 16 p/s µ + e + + ν µ +ν e µ/yr ν e /yr ν µ /yr ν µ µ + Oscillate ν µ µ Wrong Sign muons M Bonesini - INFN Milano 10

11 Advantages of Muon Storage Ring Both ν e and ν µ species in beam: A way to get well understood, highintensity source of ν e s ν e ν τ or ν e ν µ High intensity allows: Probe small mixing angles Long distances Start to see earth matter effects for oscillations involving ν e s Reach solar neutrino region with acc beams 11

12 Comparison with Conventional ν Beam M Bonesini - INFN Milano 12

13 ν - Factory Beam and Detector Parameters High Rate Beam: muon decays /yr ν rates higher than conventional beams for E storage > ~20 GeV Rate in detector E 3 High storage ring energy ~ 50 GeV Detector: Large: 10 kton Need at least µ ± id. (with beam flavor constraints). Better to also have e ± and τ ± identification ν events/gev for various µ beam energies 20 GeV 35 GeV 50 GeV M Bonesini - INFN Milano 13

14 Sensitivity of Nufact M Bonesini - INFN Milano 14

15 4. Conventional superbeams Exploit extremely intense proton sources to produce beam from π-decay Intermediate step to neutrino factory π beam necessary for µ beam Sensitivity intermediate between near-term experiments and neutrino factory Cost also intermediate Technical hill less steep to climb Proton drivers essentially designed (or existing) Radiation damage near target station may be important M Bonesini - INFN Milano 15

16 Possible Future Proton Drivers Source Place Proton Energy (GeV) Power (MW) Upgr. Booster FNAL 16 1? Upgr. NUMI FNAL GeV PS JHF ( 4) SPL CERN M Bonesini - INFN Milano 16

17 CERN/SPL Proposed: Recycle LEP RF cavities into proton linac Proton kinetic energy: 2.2 GeV Power: 4 MW Protons/s=10 16 Outlook: Feasibility study M Bonesini - INFN Milano 17

18 SPL Neutrino Beam Liquid Hg jet target 20 m decay tunnel Kaon production negligible Few ν e content E ν ~ 250 MeV M Bonesini - INFN Milano 18

19 JHF 50 GeV PS at Jaeri Approved: 50 GeV PS MW Proposed: Neutrino beamline to Kamioka (off-axis 295 km) Upgrade to 4 MW Outlook: Completion of PS in 2006/2007 M Bonesini - INFN Milano 19

20 JHF Neutrino Beams Wide-band beam Horn-focusing only Long high-energy tail Narrow-band beam Pions momentumselected with dipole Lower intensity Off-axis beam Intense, narrow Less tail than WBB 0.2% ν e around peak energy M Bonesini - INFN Milano 20

21 5. A roadmap to the neutrino factory Study to optimize target : HARP experiment at CERN Study to demonstrate the operation of a full size section of a cooling section: MICE experiment at RAL NUFACT ECFA WG to study neutrino factory and superbeam physics +. Cerenkov Tof Tpc A Layout of the Harp experiment spectrometer 21

22 Targetry Many difficulties: enormous power density pion capture Replace target between bunches: Liquid mercury jet or rotating solid target Stationary target: Proposed rotating tantalum target ring Sievers Densham 22

23 Harp at the Cern PS 2-24 GeV/c incident p beam on nuclear targets (Be, C,Al, Cu, Sn, Ta, Pb,... + Miniboone & K2K replica) Full solid angle acceptance PID for π/p separation Aims: cross sections at a 2% precision Data taking about 71 * 10 6 triggers M Bonesini - INFN Milano 23

24 Harp experiment aims HARP (Hadron Production Experiment at the PS) designed to measure with few % accuracy cross sections for hadron production of protons (2 to 15 GeV/c) on various elements necessary to calibrate Monte Carlo simulations for: the design of a nu-factory the mastering of existing nu-beams the interpretation of atmospheric nu-oscillation experiments HARP was designed, built and assembled in 17 months! M Bonesini - INFN Milano 24

25 HARP schematic layout Tof with RPC HARP consists of a barrel spectrometer (TPC) and of a forward spectrometer (NDC) to cover the full solid angle, complemented by particle-id detectors Ckov ToF e-id Ckov beam TPC Forward spectrometer Tof MWPC Target M Bonesini - INFN Milano 25

26 Cooling: the problem (transverse phase space) Problem: µ Beam pipe radius of storage ring P or x and x reduction needed: COOLING Accelerator acceptance R 10 cm, x 0.05 rad Accelerato 200 MeV π and µ after focusing M Bonesini - INFN Milano 26

27 Ionization Cooling : the principle Liquid H 2 : de/dx sol IN Beam H 2 sol rf RF restores only P // : E constant OUT M Bonesini - INFN Milano 27

28 MICE: Muon Ionisation Cooling Experiment Proposal submitted to RAL SC Solenoids; Spectrometer, focus pair, compensation coil Liquid H2 absorbers or LiH? T.O.F. I & II Pion /muon ID precise timing 201 MHz RF cavities Tracking devices: He filled TPC-GEM (similar to TESLA R&D) T.O.F. III and/or sci-fi Precise timing Measurement of momentum, angles and position Electron ID Eliminate muons that decay M Bonesini - INFN Milano 28

29 Possible locations around Europe for FAR detector 3500 km 732 km 3500 km M Bonesini - INFN Milano 29

30 Detector (one option) Magnetized iron calorimeter Charge discrimination B = 1 T R = 10 m, L = 20 m Fiducial mass = 40 kt Baseline 732 Km 3.5 x Km ν µ CC ν e CC ν µ signal 1.2 x x x x x 105 Events for 1 year M Bonesini - INFN Milano 30

31 A Simple Neutrino Factory Detector (another option US MUCOL collab) Iron sampling calorimeter ~50 kton (10X the fiducial mass of MINOS), with extruded scintillator (R&D effort at Fermilab). This implies R&D on scintillators, that is a detector technology of general interest (calorimetry, TOF, fiber tracker, ). It can be applied also outside the realm of v physics, not the case with Lar TPC or water Cerenkov Suited to θ 13 exploration at large L and E, and sign( m 2 23) M Bonesini - INFN Milano 31

32 6. The BETA-BEAM 1. Produce a radioactive ion with a short beta-decay lifetime 2. Accelerate the ion in a conventional way (PS) to high energy 3. Store the ion in a decay ring with straight sections. 4. By its β decay, ν e (ν e ) will be produced. Muons: γ~500 E cms ~34 MeV QF~15 - SINGLE flavour (ν e ) - Known spectrum/intensity - Focussed (1/γ) - Low energy (E ν = 580 Mev) 6 He Beta-: γ~150 E cms ~1.9 MeV QF~79 18 Ne Beta+: γ~250 E cms ~1.86 MeV QF~135 The quality factor QF=γ/E cms (N int α γ/ E cms ) is bigger than in a conventional neutrino factory. In addition, ion production and collection is easier. Then, X more time to accelerate. M Bonesini - INFN Milano 32

33 CERN baseline scenario Decay ring SPL Bρ = 1500 Tm B = 5 T L ss = 2500 m ISOL target SPS Decay Ring ACCUMULATOR PS Studies are made on EXISTING CERN machines. Why? Much more detailed knowledge exists, the best way to identify possible problems and limitations. M Bonesini - INFN Milano 33

34 Possible β - emitters (ν e ) Isotope Z A A/Z T 1/2 Q β (gs>gs) Q β eff. E β av. E ν av. <E_LAB> ( MeV) s MeV MeV MeV MeV (@ 450 GeV/p) 6He He Li Li Be C C N N N Ne Ne Na Na M Bonesini - INFN Milano 34

35 Anti-Neutrino Source Consider 6 He ++ 6 Li +++ ν e e - E MeV T/ s 1. The ion is spinless, and therefore decays at rest are isotropic. 2. It can be produced at high rates, i.e. 5E13 6 He/s 3. The neutrino spectrum is known on the basis of the electron spectrum. DATA and theory: <Ekine>=1.578 MeV <Eν>=1.937 MeV RMS/<Eν>=37% B.M. Rustand and S.L. Ruby, Phys.Rev. 97 (1955) 991 B.W. Ridley Nucl.Phys. 25 (1961) 483 M Bonesini - INFN Milano 35

36 Some experimental considerations The neutrino energy is controlled by the Lorentz boost γ of the parent ion Only possible backgrounds are: Detector backgrounds: single pions from NC and electrons misid as µ Atmospheric neutrinos M Bonesini - INFN Milano 36

37 Physics reach of beta beams etc (M. Mezzetto, NNN02) δ = 90 deg 99%C.L. Curves M Bonesini - INFN Milano 37

38 Nu2002 comparison chart F. Dydak GeV ~10-4 ~1 YesYes Let s Fill the BB column! M Bonesini - INFN Milano 38

39 Conclusioni La fisica delle oscillazioni di ν e l item di punta di HEP, oltre alla ricerca dell Higgs ai collider adronici I futuri sviluppi in questo campo sono dominati dallo sviluppo di nuovi fasci di neutrino (nu-fact, superbeams,...) per cui si ha un attivo programma di R&D in Europa, negli US ed in Giappone M Bonesini - INFN Milano 39