Yu. PotrebenikovYu. PotrebenikovJINR, DubnaJINR, Dubna

1313thth Lomonosov Conference Lomonosov Conference on Elementary Particle Physics, on Elementary Particle Physics,

Moscow, August 23-29, 2007Moscow, August 23-29, 2007

The The KK++ experiment at experiment at CERNCERN

P326 – NA48/3 – NA62P326 – NA48/3 – NA62

22

The The decays: a clean test of SM decays: a clean test of SM sensitive to new physicssensitive to new physics

Flavor Changing Neutral Current loop process: sFlavor Changing Neutral Current loop process: sd coupling d coupling and highest CKM suppressionand highest CKM suppression

Very clean theoretically: short Very clean theoretically: short distance contributions dominate, distance contributions dominate, hadronic matrix element can be hadronic matrix element can be related to measured quantitiesrelated to measured quantities((KK++00ee++..

SM predictions (uncertainties from CKM elements):SM predictions (uncertainties from CKM elements): BR(BR(KK++++) ) (1.6×10 (1.6×10-5-5)|V)|Vcbcb||44[[22+(+(cc--))22] ] (8.0 ± (8.0 ± 1.1)×101.1)×10-11-11

BR(BR(KKLL00) ) (7.6×10 (7.6×10-5-5)|V)|Vcbcb||442 2 ± 0.6± 0.6×10×10-11-11

Sensitive to New PhysicsSensitive to New PhysicsPresent measurement (E787/949): Present measurement (E787/949): BR(KBR(K++) = 1.47 ) = 1.47 × 10× 101010 (3 events)(3 events)

+1.30

-0.89

-

Golden modes

33

Effects of new physics on KEffects of new physics on K decaysdecays

F. MesciaCKM 2006

Effects of new physics on decays

44

Setting the bar for future Setting the bar for future experiments experiments

P3

26

P3

26

E787/949E787/949

BR(KBR(K++) = 1.47 ) = 1.47 ×10×101010

+1.30-0.89

SM

F. MesciaCKM 2006

100 100 eventseventsMean:

E787/949

55

September 2005: presented at CERN SPSCSeptember 2005: presented at CERN SPSCDecember 2005: R&D endorsed by CERN Research BoardDecember 2005: R&D endorsed by CERN Research BoardStart of the Gigatracker projectStart of the Gigatracker projectStart of test beams at CERN in 2006Start of test beams at CERN in 20062007: prototypes construction and test at CERN and Frascati 2007: prototypes construction and test at CERN and Frascati beamsbeams2008 – 2010: Technical design and construction2008 – 2010: Technical design and construction2011 - Start of data taking2011 - Start of data taking

Proposal to Measure the Rare Decay Proposal to Measure the Rare Decay at the CERN SPS (P326)at the CERN SPS (P326)

CERN, Dubna, Ferrara,CERN, Dubna, Ferrara,Florence, Frascati, Mainz,Florence, Frascati, Mainz,Merced, Moscow, Naples,Merced, Moscow, Naples,Perugia, Protvino, Pisa,Perugia, Protvino, Pisa,Rome, Saclay, San Luis Rome, Saclay, San Luis

Potosi, Potosi, Sofia, Triumf, TurinSofia, Triumf, Turin

CERN-SPSC-2005-013 SPSC-P-326

Schedule

Located in the same hall of NA48Located in the same hall of NA48

66

Base of the NA62 (NA48/3)Base of the NA62 (NA48/3)

O(100) K++events ~ 10% background

1) Physics: BR(SM) = 8×10-11

Acceptance 10%Acceptance 10%KK decays ~10 decays ~101313

Kaon decay in flight techniqueKaon decay in flight techniqueIntense proton beam from SPSIntense proton beam from SPSHigh energy K (PHigh energy K (PKK = 75 GeV/c) = 75 GeV/c) Kaon IDKaon ID

Kinematical rejectionKinematical rejection

Veto and particle IDVeto and particle ID

Kaon 3-momentum: beam trackerKaon 3-momentum: beam trackerPion 3-momentum: spectrometer Pion 3-momentum: spectrometer // detection: calorimeters detection: calorimetersCharged veto: spectrometerCharged veto: spectrometer///e separation: RICH/e separation: RICH

2) Budget: …Use as much as possible Use as much as possible the existing the existing NA48 NA48 infrastructuresinfrastructures

Be pragmaticBe pragmatic

KK+

m2miss=(PKP)2

77

BackgroundsBackgrounds

92% of total background

Allows us to define a signal region K+ +0 forces us to split it into

two parts (Region I and Region II)

Span across the signal region Rejection must rely on veotes

Kinematically constrained Not kinematically constrained

8% of total background

88

K+→ (K)

Largest BR: 63.4%Need ~10-12 rejection factor• Kinematics: 10-5

• Muon Veto: 10-5 MAMUD• Particle ID: 5×10-

3RICH

K+→ (K)

2nd largest BR: 20.9%Need ~10-12 rejection factor• Kinematics: 5×10-3• Photon Veto: 10-5 per photon

Assuming the above veto inefficiencies and an acceptance of 10%, a S/B > 10 is obtained if

mmiss2 ~ 8×10-3GeV2/c4

Resolution requirements:

P< 1 %, PK 0.3 %, K 50-60 μrad

Largest background rejectionLargest background rejection

99

Layout of the experimentLayout of the experiment

+

10-6 mbar

+

VACUUM10-6 mbar

50 MHz

800 MHz 11 MHz

K+ ~ 75 GeV

P proton = 400 GeV/cProton/pulse 3.3×1012 (3.3×NA48/2)

Duty cycle 4.8/16.8 s

P Kaon = 75 GeV/c (P/P = 1.1%)Fraction of Kaons ~ 6.6%Negligible amount of e+

Beam acceptance = 12 str (25× NA48/2)Area @ beam tracker = 58×24 mm2

Integrated average rate = 760 MHzKaon decays / year = 4.8 × 1012

1010

The Tracking system: GigatrackerThe Tracking system: Gigatracker

Low Low X/XX/X00 not to spoil the beam not to spoil the beam

Good space resolution to match the Good space resolution to match the downstream tracker resolutiondownstream tracker resolution

200 Si m sensor + 100 Si m chip

300×300 m pixels(PK)/PK ~ 0.22%(K) ~ 16 rad(

(

Excellent time resolution Excellent time resolution needed for K+/needed for K+/+ association: + association: (t)~200 ps(t)~200 ps per station per station

Readout chip bump-bonded on the sensor (0.13 m technology)

The Gigatracker (i.e. the beam tracker)

Rate: 760 MHz (charged particles) ~60MHz/cmRate: 760 MHz (charged particles) ~60MHz/cm22

3 Si pixel stations across the 2nd achromat: size 60 × 27 mm2

Readout chip: 1st MPW in 0.13Readout chip: 1st MPW in 0.13m technologym technology is ready to test is ready to test (results by September)(results by September)

Si diode irradiation testsPrototype wafers (200µm thick) produced by itc-IRST using ALICE pixel layout3 mm × 3 mm and 7 mm × 7 mm test-diodesTest diodes irradiated with n and p (Ljubljana, CERN)Fluences: 1E12 to 2E14 1MeV n cm-2 (range P326)Pre and post irradiation measurements (annealing) to study diode characteristics

1111

The Tracking system: Double The Tracking system: Double SpectrometerSpectrometer

6 chambers with 16 layers of straw tubes each

Low X/XLow X/X00

Good space Good space & angle resolution& angle resolution

Redundant p Redundant p measurementmeasurement

Veto for chargedVeto for charged particlesparticles

130 130 m per hitm per hit

2 magnets

The Double Spectrometer (i.e. the downstream tracker)

Rate: ~ 45 KHz per tube (max 0.8 MHz)Rate: ~ 45 KHz per tube (max 0.8 MHz)

5 cm radius beam hole displaced in the bending plane

8.8

m

7.2

m

2

.3 m

In vacuum, X/X0~0.1% per view

1212

Straw prototypeStraw prototype

Chosen technology: ultrasound welded gilded mylar tube (36 Chosen technology: ultrasound welded gilded mylar tube (36 m, D=10 mm, L=2.3 m)m, D=10 mm, L=2.3 m)48 straw prototype has been produced in Dubna48 straw prototype has been produced in DubnaTests on gas leakageTests on gas leakageTests on tube expansion in vacuum Tests on tube expansion in vacuum Prototype assembled & cosmic ray tests Prototype assembled & cosmic ray tests

October 2007: October 2007: Prototype integration in NA48 set-up and test on a beamPrototype integration in NA48 set-up and test on a beam

Design, construction and test of a Straw prototype (Dubna, CERN)Design, construction and test of a Straw prototype (Dubna, CERN)

1313

The Particle Identification system: The Particle Identification system: CEDARCEDAR

CEDAR: existing differential Cerenkov counter at CERN to be placed on the beam Tagging the kaon to keep the Tagging the kaon to keep the

beam background under controlbeam background under controlMinimal material budgetMinimal material budgetGood time resolutionGood time resolution

HH22 instead of Ne instead of NeNew phototubesNew phototubes

The CEDAR (i.e. the kaon ID)

CEDAR W-type filled with NeCEDAR W-type filled with Ne tested tested at CERN in November 2006, using a at CERN in November 2006, using a 100 GeV hadron beam with 10100 GeV hadron beam with 1055 – 10 – 1077 ppp (CERN, Firenze, Perugia).ppp (CERN, Firenze, Perugia).

Beam Composition

00,10,20,30,40,50,60,70,8

1650 1700 1750 1800 1850 1900 1950 2000 2050

Pressure

%

Plan:Plan: to test of fast to test of fast photomultipliers photomultipliers using Cerenkov using Cerenkov light.light.

pion

kaon

proton

1414

The Particle Identification system: RICHThe Particle Identification system: RICH

18 m long tube (2.5 m diamater) filled with Ne @ 1 atm, two 17m focal length mirrors

>3>3 pion/muon pion/muon separation @ 35 GeV/c separation @ 35 GeV/c (13 GeV/c threshold for (13 GeV/c threshold for ))

Time resolution 100 ps Time resolution 100 ps (track timing)(track timing)

VelocityVelocityspectrometerspectrometer(redundancy)(redundancy)

High granularity(2000 PMTs)Small pixel size(18 mm PMT)

Phototubes with very good (t)

The RICH (i.e. the pion ID)

1515

RICH prototypeRICH prototype

Design, construction and test of a RICH prototype (CERN, Design, construction and test of a RICH prototype (CERN, Firenze, Perugia)Firenze, Perugia)

Full length prototype (17 m, 0.6 m diamater, Full length prototype (17 m, 0.6 m diamater, stainless steel tube at CERN) stainless steel tube at CERN)Mirror built, delivered and under test in FirenzeMirror built, delivered and under test in FirenzeEndcap with 96 Hamatsu PMs readout Endcap with 96 Hamatsu PMs readout through Winston’s cones through Winston’s conesPMs tested at SPS (2006) and Firenze (with laser)PMs tested at SPS (2006) and Firenze (with laser)

Measured Measured Full Width Half MaximumFull Width Half Maximum ( (FWHM) FWHM) per single per single per phototube: per phototube: 390ps390ps (150 ps (150 ps electronics and 110 ps laser included)electronics and 110 ps laser included)

FWHM 0.375 ps

t ns

November 2007: November 2007: prototype integration prototype integration into the NA48 set up into the NA48 set up and test with beam and test with beam

1616

The Veto systemThe Veto system

Large angle (10, 50 mrad): Rings calorimeters (in vacuum)Rate: ~4.5 MHz (Rate: ~4.5 MHz () + ~0.5 MHz () + ~0.5 MHz () ) 1010-4-4 inefficiency for E inefficiency for E in 0.05,1 GeV in 0.05,1 GeV1010-5-5 inefficiency for E inefficiency for E>1 GeV >1 GeV

20 X/X0 Lead scintillator tiles orLead scintillator fibers (KLOE-like) Medium angle (1, 10 mrad): LKr

calorimeterRate: ~8.7 MHz (Rate: ~8.7 MHz ()+~4 MHz ()+~4 MHz () )+~3 MHz () )+~3 MHz ())1010-4-4 inefficiency for E inefficiency for E in 1,5 GeV in 1,5 GeV1010-5-5 inefficiency for E inefficiency for E>5 GeV >5 GeV

Small angle (<1 mrad): Shashlik technologyRate: 0.5 MHz (Rate: 0.5 MHz ())

1010-5-5 inefficiency (high energy photons) inefficiency (high energy photons)

New Readout

Extruded scintillator – lead sampling calorimeter 6 m long + magnet for beam deflectionRate: ~7 MHz (Rate: ~7 MHz ()+~3 MHz ()+~3 MHz ())1010-5-5 inefficiency for inefficiency for detection detection

Deviate the beam out from the SACDeviate the beam out from the SAC

em/hadronic cluster separation.Sensitivity to the MIP5Tm B field in a 30×20cm2 beam hole

Photon vetoes

Muon veto

1717

Large angle Photon VetoesLarge angle Photon Vetoes

KLOE-type lead/scintillating fiber: prototype constructed in KLOE-type lead/scintillating fiber: prototype constructed in FrascatiFrascati1 mm diameter scintillating fibers, 1 mm diameter scintillating fibers, 0.5 mm thick lead foils. 0.5 mm thick lead foils.

Readout granularity: 18 cellsReadout granularity: 18 cellsVery well known and tested technologyVery well known and tested technologyUnder test at the Frascati BTFUnder test at the Frascati BTF

16.8 cm 8.2 cm

All fiber: 8 X0

Fibers+lead wires:

9 X0

Studies of the efficiency of detectors Studies of the efficiency of detectors built with this technology availablebuilt with this technology availableFermilab prototype under test at BTFFermilab prototype under test at BTF

Outgassing tests performed at CERN Outgassing tests performed at CERN on detectors built with same on detectors built with same technology: they can be placed in the technology: they can be placed in the vacuum of the decay region (10vacuum of the decay region (10 -6-6 mbar)mbar)

Lead scintillator tiles

1818

Large angle Photon Vetoes testsLarge angle Photon Vetoes tests

ee

Test beam activity at BTF in Test beam activity at BTF in FrascatiFrascati (Frascati, Napoli, Pisa, Roma)(Frascati, Napoli, Pisa, Roma)

ee-- beam (300-500 MeV/c) beam (300-500 MeV/c)Both calorimeter prototypes under testBoth calorimeter prototypes under test11stst step: test with electrons step: test with electrons22ndnd step: test with photons step: test with photons

Test beam periods: March, April, June 2007Test beam periods: March, April, June 2007The main result:The main result: both prototypes show both prototypes show goodgoodcharacteristics: inefficiency ~ 10characteristics: inefficiency ~ 10-5 -5 for for E=500,E=500,200-350 MeV (10200-350 MeV (10-4-4 for LG due to statistics). for LG due to statistics).Good energy resolution is obtained for fiber Good energy resolution is obtained for fiber

calorimeter:calorimeter:

It is necessary to understand the beam It is necessary to understand the beam background and to make background and to make calibrations of the prototypescalibrations of the prototypes

%63.4)(

%88.5)(

GeVEE

E

1919

Measurement of the inefficiencyMeasurement of the inefficiencyKK++ data taken in a dedicated NA48 data taken in a dedicated NA48 test run in 2004 using Ktest run in 2004 using K++++00

LKr calorimeterLKr calorimeter

Tagged Tagged using an SPS electron beam (2006) using an SPS electron beam (2006)

Inefficiency measured for EInefficiency measured for E > 2.5 GeV > 2.5 GeV> 10 GeV, > 10 GeV, < 10 < 10-5-5 confirmed confirmed< 10 GeV analysis in progress< 10 GeV analysis in progress

Consolidation of the readoutConsolidation of the readoutCustom boards (FPGA based) sending data directly to PC FarmCustom boards (FPGA based) sending data directly to PC FarmTest of the new electronics in 2007 NA48 runTest of the new electronics in 2007 NA48 run

< 10< 10-5-5 (@90% C.L., E(@90% C.L., E>10 >10 GeV)GeV)

electronelectron

Energy deposition in LKr

X LKr cm

En

erg

y G

eV

z

x

vacuum

e beam25 GeV/c

Bremsstrahlung

Kevlar window

Drift chambers

Magnet LKr

e-

He

2020

Preliminary sensitivity studiesPreliminary sensitivity studies

Acceptance (60 m fiducial

volume): Region I: 4% Region II: 13% Total: 17%

To be reduced because of losses due dead time, reconstruction inefficiencies…

Simulation of the P-326 apparatus

Acceptance ~ 10% is achievable

Region I and II Momentum range: 15 < P < 35 GeV/c

Against muons RICH operational reasons Plenty of energy in photon vetoes

2121

Analysis: background rejectionAnalysis: background rejection

Events/yearEvents/year TotalTotal Region IRegion I Region Region IIII

Signal Signal (acc=17%)(acc=17%) 6565 1616 4949

KK++++00 2.72.7 1.71.7 1.01.0

KK++++ 1.21.2 1.11.1 <0.1<0.1

KK++ee++++ ~2~2 negligiblnegligiblee

~2~2

Other 3 – track Other 3 – track decaysdecays

~1~1 negligiblnegligiblee

~1~1

KK++++00 1.31.3 negligiblnegligiblee

1.31.3

KK++++ 0.50.5 0.20.2 0.20.2

KK++ee++((++))00, , othersothers

negligibnegligiblele

Total bckg.Total bckg. <9<9 3.03.0 <6<6

S/B ~ 8 (Region I ~5, Region II ~9)

2222

TriggerTrigger

LevelLevel L0 “hardware” L0 “hardware” L1-L2 “software” L1-L2 “software”

InputInput ~10 MHz~10 MHz 1 MHz1 MHz

OutputOutput 1 MHz1 MHz OO(KHz)(KHz)

ImplementatImplementationion

Dedicated Dedicated hardwarehardware

TDAQ farmTDAQ farm

ActionsActions RICH minimum RICH minimum multiplicity, multiplicity,

Muon vetoing, Muon vetoing, LKr vetoingLKr vetoing

L1 = single sub-L1 = single sub-detectorsdetectors

L2 = whole eventL2 = whole event

Main work on possible solutions for the L0 hardwareMain work on possible solutions for the L0 hardwareTELL-1 board (LHCb) based implementation for all non FADC sub TELL-1 board (LHCb) based implementation for all non FADC sub detectorsdetectorsDesign of a new 100 ps TDC daughter-card (RICH, Straws, MAMUD,…)Design of a new 100 ps TDC daughter-card (RICH, Straws, MAMUD,…)Two prototypes under study (Mainz and Pisa)Two prototypes under study (Mainz and Pisa)

A possible scheme:A possible scheme:

2323

Other physics opportunitiesOther physics opportunities

P-326 Kaon Flux ~100 times NA48/2 Kaon P-326 Kaon Flux ~100 times NA48/2 Kaon FluxFlux

Other physics opportunities can be Other physics opportunities can be addressed:addressed:

Lepton – flavor violation (Lepton – flavor violation (started with a run 2007started with a run 2007): ): KKe2e2/K/K22,K,K++++++ee--, K, K++--++ee++

Search for new low mass particles:Search for new low mass particles: KK++(light RH neutrinos)(light RH neutrinos) KK++++00P P (pseudoscalar sGoldstino)(pseudoscalar sGoldstino)

Hadron spetroscopyHadron spetroscopy

……

2424

ConclusionsConclusions

To search for new physics using rare Kaon decays To search for new physics using rare Kaon decays P-326 experimentP-326 experiment is proposed and prepared for is proposed and prepared for measurement of the Br(Kmeasurement of the Br(K++++) with a ~10% ) with a ~10% accuracy accuracy (& for other physics opportunities(& for other physics opportunities))

General design is mostly defined. Overall simulation Overall simulation and performances are under review.and performances are under review.

The R&D program The R&D program is well advanced: construction of is well advanced: construction of detector prototypes and tests are in progress (in detector prototypes and tests are in progress (in some cases - completed). Important results should some cases - completed). Important results should be obtained be obtained by the end of 2007by the end of 2007

The new experimentThe new experiment should be able to reach a should be able to reach a ~10~10--

1212 sensitivity per event sensitivity per event at at an existing machine and an existing machine and employing the infrastructures of an existing employing the infrastructures of an existing experimentexperiment. .