Rare decay Opportunities at U-70 Accelerator (IHEP, Protvino) Experiment KLOD Joint Project : IHEP,Protvino JINR,Dubna INR, Moscow, RAS

3 STATE RESEARCH CENTER OF RUSSIA INSTITUTE FOR HIGH ENERGY PHYSICS

theoretically Rare FCNC process Purely CP-Violetting (Littenberg, 1989) Totally dominated from t-quark  Computed in QCD (Buchalla, Buras, 1999)  Small corrections due to m t is known from K +   0 e + e (K e3 )  No long distance contribution (Rein, L. M. Sehgal, 1989; Marciano, Z. Parsa 1996) SM: Br ~ η 2, CP violating parameter (Buchalla, Buras, PR, 1996) Sensitive to the new heavy objects  New physics Theoretically clean process, ~1% SM: Br = (2.8±0.4)×10 −11 (Buras et al., hep-ph/ )

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10 Experimental challenge. Must-do experiment signature: π 0 -signal + “nothing” At least 2 charged or 4 γ’s -- veto inefficiency ~ full veto covered π 0 in 34% of decays -- P T cut (231MeV/c) Interaction with gas -- high vacuum Strategy: 2 γ’s in Ecal No veto-signal Construct π 0 from 2 γ’s -- reconstruct vertex -- reconstruct P T (narrow beam approach)

K L beam at U-70 IHEP Beam requirements -- very narrow (R<5cm) and well collimated -- high P T balanced -- high intensity (~10 8 K L /pulse) -- mean K L energy ~10 GeV -- minimal contamination of neutral unwanted particles (neutrons/K L < 10) Sketch design completed ! K L beam optimization conditions GeV p/cycle (slow extraction); -- Cu-target 25см (80% interactions); - 35 mrad extraction angle; - 5 cm Pb-converter: - steel collimators

K L beam at U-70 IHEP Beam requirements -- very narrow (R<5cm) and well collimated -- high P T balanced -- high intensity (~10 8 K L /pulse) -- mean K L energy ~10 GeV -- minimal contamination of neutral unwanted particles (neutrons/K L < 10) Sketch design completed ! K L beam optimization conditions GeV p/cycle (slow extraction); -- Cu-target 25см (80% interactions); - 35 mrad extraction angle; - 5 cm Pb-converter: - steel collimators

K L beam. Calculated parameters Background & Fluxes per spill

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

KLOD Detector Layout Vacuum requirement: ~(10 – –4 ) torr inside tank ~ 10 –7 torr inside internal membrane Another solutions under study Forward CalorimeterMain VetoVeto HodoscopeForward Veto SectionBackward Veto Section

Main Veto (1) “Shashlyk” – calorimeter (0.3mm Pb + 1.5мм molding Scint.) photons per 1 GeV  -shower 5.5 ph.e – per single Sc. plate for mip 18 ph.e – per 1 MeV of “visible” energy  E /E  3%/sqrt(E) Module size along the beam Module size across the beam Scintillator thickness Lead thickness Radiation length, X 0 Module length (active part) Module full length Module weight Fibers length (per module) # modules in Main Veto Fibers length in Main Veto 300 mm 200 mm 1.5 mm mm 35.5 mm 500 mm 600 mm 80 kg 268 m km Segmentation along the beam – 100 mm Segmentation across the beam – 200 mm 0.55 mm for the rear part mm for the rear part ( ) mm, (10 + 8) X 0 Without photodetector All loops including (28 – across beam) х (50 – along beam) Loops Mirrored

Main Veto (1) “Shashlyk” – calorimeter (0.3mm Pb + 1.5мм molding Scint.) photons per 1 GeV  -shower 5.5 ph.e – per single Sc. plate for mip 18 ph.e – per 1 MeV of “visible” energy  E /E  3%/sqrt(E) Module size along the beam Module size across the beam Scintillator thickness Lead thickness Radiation length, X 0 Module length (active part) Module full length Module weight Fibers length (per module) # modules in Main Veto Fibers length in Main Veto 300 mm 200 mm 1.5 mm mm 35.5 mm 500 mm 600 mm 80 kg 268 m km Segmentation along the beam – 100 mm Segmentation across the beam – 200 mm 0.55 mm for the rear part mm for the rear part ( ) mm, (10 + 8) X 0 Without photodetector All loops including (28 – across beam) х (50 – along beam) Loops Mirrored

Main Veto (2)

In Beam Veto Calorimeter 1-st idea :to use Cherenkov light quartz fibers are only sensitive to em shower component CMS HF: e/h ~ 5, NIM A399 (1997) nd idea: Dual Readout (Scint.+Ch.) DREAM calorimeter, NIM A536 (2005) 29 Purpose is to measure f em event by event & eliminate dominant source of fluctuations for hadrons. They succeed ! Hadron Blind Calorimeter ? Not our goal ! But look at Ch/Sc signals ratio & its behavior in transverse and longitudinal directions Possible problem : not enough Ch. light => 45 deg. turn => more quartz fibers (more loose structure) The goal is not to measure E but to identify γ’s Not Hadron-Blind but Hadron-Distinguishable Calorimeter Suitable for our goal prototype is under construction

In Beam Veto Calorimeter 1-st idea :to use Cherenkov light quartz fibers are only sensitive to em shower component CMS HF: e/h ~ 5, NIM A399 (1997) nd idea: Dual Readout (Scint.+Ch.) DREAM calorimeter, NIM A536 (2005) 29 Purpose is to measure f em event by event & eliminate dominant source of fluctuations for hadrons. They succeed ! Hadron Blind Calorimeter ? Not our goal ! But look at Ch/Sc signals ratio & its behavior in transverse and longitudinal directions Possible problem : not enough Ch. light => 45 deg. turn => more quartz fibers (more loose structure) The goal is not to measure E but to identify γ’s Not Hadron-Blind but Hadron-Distinguishable Calorimeter Suitable for our goal prototype is under construction

In Beam Veto Calorimeter 1-st idea :to use Cherenkov light quartz fibers are only sensitive to em shower component CMS HF: e/h ~ 5, NIM A399 (1997) nd idea: Dual Readout (Scint.+Ch.) DREAM calorimeter, NIM A536 (2005) 29 Purpose is to measure f em event by event & eliminate dominant source of fluctuations for hadrons. They succeed ! Hadron Blind Calorimeter ? Not our goal ! But look at Ch/Sc signals ratio & its behavior in transverse and longitudinal directions Possible problem : not enough Ch. light => 45 deg. turn => more quartz fibers (more loose structure) The goal is not to measure E but to identify γ’s Not Hadron-Blind but Hadron-Distinguishable Calorimeter Suitable for our goal prototype is under construction

Monte-Carlo Resolutions -- σ(Z) ≈ 15 cm (without beam contribution) Dominated by FCal energy resolution -- σ(P T ) ≈ 6 MeV/c Defined by beam angular spread

For 1 SM decay K L    0.1 Br = 5.7 x K L   0  0 ~ 0.26 Br = 9.1 x Max(Pt)=209 МэВ/c K L   0  0  0  0.1 Br = 21.6% Max(Pt)=139 МэВ/c K L   - е +  0.1 Br = 38.7% Main cuts E  (1), E  (2) > 0.15 GeV better FCal performances, γ’s from excitation E  (1), E  (2) < 6 GeV Pt > 120 MeV/c Reconstructed Vertex inside Main Decay Volume γ’s pointed to the reconstructed Vertex (+/- 0.5 m) works for γ’s not from one π 0 Energy gravity Center > 20 cm from beam axis Dist(γ1-γ2) > 15 cm accidentals, γ’s from different π 0 ’s Background & Sensitivity Estimation Acceptance – 18 (15) % 4.8% K L decays in Main 10 8 (5.4×10 7 ) K L /spill 10 days sensitivity (~ 10 4 spills/day) 10×(10 4 )×( 10 8 )×(4.8×10 -2 )×(1.8×10 -1 )×Br(2.8× ) ≈ 2.4 events 10×(10 4 )×(5.4×10 7 )×(4.8×10 -2 )×(1.5×10 -1 )×Br(2.8× ) ≈ 1.1 events

Summary. It is possible to make registration of K 0 → π 0 νν(bar) decays at IHEP setup. Sensitivity of setup allows for reasonable time (100 days) to register about 30 (SM) decays at a level of a background nearly 9 decays. R&D for production and test prototypes of the basic detectors is necessary. Some of detectors were tested and the results coincide with calculations. The further simulation for more exact calculation of signals and background processes is necessary.