Project of the Super Charm-Tau Factory in Novosibirsk

Transcription

1 Project of the Super Charm-Tau Factory in Novosibirsk Sergey Kononov Budker Institute of Nuclear Physics & Novosibirsk State University Talk at the 17th Lomonosov Conference on Elementary Particle Physics August 24,

2 Introduction Prehistory 1970 th VEPP-3M GeV in c.m., 1990 th th Project of Tau-Charm Factory with luminosity up to cm -2 s th GeV in c.m. Current state of the art The only realized cτ-factory: BEPCII/BESIII with designed luminosity of cm -2 s -1 Some Charm and Tau physics is studied at В-factories in B-decays and ISR (implemented at BaBar by collaborators from BINP). Looking forward to SuperKEKB. PANDA project at FAIR with wide Charm-Tau physics program: after 2021 Motivation for Super cτ factory (SCTF) with L cm -2 s -1 It would provide higher statistics than BESIII More clean statistics near production thresholds than SuperKEKB and PANDA Possibility of the longitudinal beam polarization for polarized τ production Recent techniques in boosting e + e collider luminosity (Crab Waist scheme) 2

3 SCTF energy region: 2-5 GeV in c.m. R σ(e e hadrons) σ(e e μ μ ) Estimate for 1 year at SCTF L = 1 ab -1 2E, GeV Number of states J/ψ ψ(2s) D D D s D s D D s ττ Λ c + Λ c DD DD D D s s D s D s c c c c 3

4 Charmonium Spectroscopy Decays ψ decays as a light meson factory: study of light quarks and search for exotics (glueballs, hybrids) Rare ψ decays XYZ charmonium-like mesons τ-lepton physics Spectral functions Lepton universality tests Lorentz structure test in τ lν l ν τ CP violation LF violation Physics program at SCTF D mesons Spectroscopy (Semi)leptonic decays Rare decays D D mixing CP violation Charmed baryons Branchings Formfactors Semileptonic decays CP violation 4

5 Charmonium Accessible statistics Direct production of 1 mesons: J/ψ ψ(2s) 10 9 ψ(3770) 10 8 ψ(4040), ψ(4160), ψ(4415) 10 7 Y(4260), Y(4360), Y(4660) In decays: J/ψ γη c (1S) ψ(2s) γχ cj (1P) 10 8 ψ(2s) π 0 h c (1P) ~10 8 ψ(2s) γη c (2S) These states are also a copious low background source of light mesons. 5

6 Rare J/ψ decays N(J/ψ) ~ per year Weak decays: J ψ D s lν l, D s ρ +, D s π + + c. c. ; Br~(3 4) 10 9 cc ss via W exchange with C violation: J ψ φφ; Br~10 8 NP search in SM-suppressed S=0 decays: J ψ D 0 ρ 0, D 0 π 0 ; Br~10 11 NP search in LFV decays: J ψ l l NP due to c-quark EDM: search for CP violation in J ψ γφφ Search for light glueballs (gg) and hybrids (qqg) 6

7 Charmed mesons spectroscopy D + D D 0 D 0 D D D s + D s D s + D s E, GeV σ max (ee DD), nb ~6.7 ~0.25 ~0.9 D (s)j states are produced in e + e D (*) D (s)j with σ~ GeV SCTF can produce D pairs and 10 9 D s pairs per year 7

8 Advantages of D meson study at SCTF in comparison with B factories Charged and neutral particle multiplicity at s=3.77 GeV 2 times lower than at 10.6 GeV Pair production (e + e DD) allows one to use double tag method when one D meson is fully reconstructed while the other is studied. Possibility of additional kinematic constrains useful for semileptonic decay reconstruction. Coherent production of D pairs allows one to use quantum correlation for studying D D mixing, CP violation, measuring strong phases, probability of decays to CP eigenstates 8

9 CPV search in D decays A CP = Γ D f Γ( D f) Γ D f + Γ( D f) Three contributions for neutral D 0 : direct CPV in decay, CPV in D D mixing, CPV in interference of mixing and decay SM predicts max. CPV in D decays at the level A CP = (1 3) 10-3 for CS decays. CPV in CF and DCS decays is much smaller. Observation of CPV in CF and DCS decays would indicate NP except D K s. A CP (D + K s + ) = (3.32±0.06) 10-3 from CPV in K. Best measurements as of 2014 Mode Experiment Year A CP, % D 0 K + K CDF ±0.22±0.09 D 0 + CDF ±0.24±0.11 D + K 2 + CLEO ±0.4±0.9 D + K s + 0 CLEO ±0.9±0.3 D + K s + BELLE ±0.094±0.067 Sensitivity to CPV asymmetry at SCTF will be about

10 τ physics ee ττ LFV decay τ μγ Current limit Br < (BaBar) ~10 10 τ pairs can be accumulated at SCTF for this study giving sensitivity to τ μγ of 10 9 Good background conditions in comparison with SuperKEKB (no ISR photon) Special run near threshold: 3.55 GeV, =0.1 nb, N =10 8 Advatages: τ s are produced at rest kinematic constraint for hadronic decay very clean data sample Non- background measured below threshold Program: High precision measurement of BF and hadronic spectral functions e / / /K lepton universality s m s, V us Study of Lorentz structure of lepton decay 4 Michel parameters, two depend on τ polarization 10

11 Search for CPV in τ decays CP violation new physics, charged Higgs Described by two amplitudes with different weak and strong phases τ K S π ν τ, A CP = τ K π 0 ν τ Observables: Rate asymmetry: Γ(τ + f + ) Γ(τ f ) ~ sinδ sinφ Modified rate asymmetry ~sinδ sinφ Triple product asymmetry σ (p 1 p 2 )~cosδ sinφ (σ τ polarization vector, p i hadron momenta) Beam polarization may increase sensitivity by several times 11

12 Collider scheme 12

13 Main collider parameters Energy 1.0 GeV 1.5 GeV 2.0 GeV 2.5 GeV Circumference Emittance hor/ver Damping time hor/ver/long 780 m 8 nm/ % coupling 30/30/15 ms Bunch length 16 mm 11 mm 10 mm 10 mm Energy spread Momentum compaction Synchrotron tune RF frequency 508 MHz Harmonic number 1300 Particles in bunch Number of bunches Bunch current Total beam current 390 (10% gap) 4.4 ma 1.7 A Beam-beam parameter Luminosity E beam = GeV L = 10 2 GeV Longitudinal polarization of IP Energy calibration by CBS Two rings Crab Waist collision scheme Sub-mm β * 5 Siberian snakes for polarization e + source Polarized e source 2.5 GeV linac 50 Hz injection Two bunch acceleration (e, e + ) 13

14 Crab Waist collisions with Large Piwinski Angle 1. P.Raimondi, 2nd Workshop on Super B-Factory, March P.Raimondi, D.Shatilov, M.Zobov,. Beam-Beam Issues for Colliding Schemes with Large Piwinski Angle and Crabbed Waist, LNF IR, Feb. 2007, e-print: physics/ e+ x 2 x / Y e- L = γ 2er e I ξ y β y 1 + σ y σ x 1 + φ 2 2 z * 2 z z 2 x φ = σ z tan θ 60 mrad σ x 2 β y = 0.2 mm (6 10 mm, B factories) ξ y = 0.15 (0.05, B factories) 100x luminosity boost without shortening bunches and increasing beam current 14

15 Implementation of Crab Waist scheme Crab Waist collision scheme was successfully tested at DAФNE (LNF) in 2008 Crab Waist scheme will be used at SCTF 15

16 Positron injector 50 Hz Extraction N = e + /s 510 MeV 2 GeV Linac 16

17 Polarized electron source Beam polarization 60 80% (90%) Cathode voltage 100 kv Photocathode type Strained InGaAsP Laser type Ti Sapphire Light wavelength nm Laser power in a pulse 200 W Pulse duration 2.1 s Repetition rate 1 Hz (50 Hz) Max. current from a gun 150 ma Operational current ma Photocathode lifetime hours Polarized electron source produced by BINP for AmPS 17

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19 Location 19

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21 Требования к детектору Для выполнения намеченной физической программы потребуется создание универсального магнитного детектора с полем 1Тл. Детектор должен иметь: Предельное импульсное разрешение для заряженных частиц и разрешение по энергии гамма-квантов Система идентификации с рекордными для существующих и строящихся детекторов параметрами. Выделение распада требует надежное / разделение до импульсов 0.8 ГэВ/с 21

22 SCTF detector Main requirements Charged particle detection with good momentum resolution γ detection with highest possible energy resolution PID system with a capability of μ/π separation Very high data flow rates (up to 500 khz) Radiation hard technologies 1. Vertex detector TPC with GEM readout 2. Drift chamber BaBar-like DCH 3. FARICH PID system BINP R&D 4. EM calorimeter Pure CsI 5. Magnet coil 1T superconducting solenoid 6. Yoke and muon system 22

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24 Counting rates J/ψ ψ(2s) ττ ψ(3770) ττ Λ c Λ c E cm, MeV σ obs, nb ~1450 ~ ~ f, 10 3 s Background processes Cosmics, 10 3 s -1 2 Hadrons, 10 3 s BhaBha, 10 3 s The higher rate of physical triggers are expected at the J/ψ peak ~ 250 khz 24

25 Computing infrastructure 25

26 FARICH Focusing Aerogel RICH Single ring option Multi-ring option First sample of 4-layer aerogel by BIC 3-layer aerogel 115x115x41 mm 3 Focusing aerogel improves proximity focusing design by reducing the contribution of radiator thickness into the Cherenkov angle resolution Multi-layer monolith aerogels are produced by the Boreskov Institute of Catalysis in coop. with BINP since In 2012 we succeeded in production of continuous density gradient aerogels. T.Iijima et al., NIM A548 (2005) 383 A.Yu.Barnyakov et al., NIM A553 (2005) Project of the Super Charm-Tau Factory at Novosibirsk

27 FARICH PID system MC: μ/π separation (σ) μ momentum range for τ μγ at E cm =4.2GeV μ/π/k/p separation in the momentum range not covered by DC (de/dx) and muon system Radiator: 4-layer aerogel with n max =1.07 Total area: 17 m 2 Photon detector: SiPM (MPPC, DPC, ) Total area: 21 m 2 ~10 6 pixels with 4mm pitch Cooling to reduce dark current Readout: FPGA-based TDC or Digital Photon Counter (Philips) Workshop on Tau Charm at High Luminosity, May

28 FARICH prototype beam test CERN PS/T10 beam channel, June 2012 Philips DPC array 20x20 cm 2 Sensors: DPC x48 pixels 3.2x3.9 mm 2 (amplitude channels) 576 timing channels: 4 pixels per on-chip TDC 4 levels of FPGA readout Operated at -40 C Ring image e 4-layer aerogel radiator n max = Thickness 37.5 mm Calculated focal distance 200 mm Hermetic container with acrylic window to avoid moisture condensation on aerogel μ/π: 1 GeV/c Workshop on Tau Charm at High Luminosity, May

29 Current status Exciting physics program has been drafted. Conceptual design of the SCTF was prepared and published in Total cost of the project is estimated at ~436 M (as of 2011) including already spent ~40 M on the injector facility and civil construction The project received expressions of support from the European Committee for Future Accelerators (ECFA), Rolf Heuer (CERN), Atsuto Suzuki (KEK), Martin L. Perl (SLAC), high scores by the international expertise carried out for 6 Russian mega-science projects in scientists from 20 institutions around the world expressed interest in the SCTF project in Other two experts assigned by the European Commission in 2013 gave a positive esteem to the project. The project is still not approved by the Russian government. Building and tunnel construction is slowly advancing. 29