25/5/2007giuseppe ruggiero, kaon 20071 the k + + experiment at cern giuseppe ruggiero sns &...

25/5/2007 Giuseppe Ruggiero, Kaon 2007 1

The K++ experiment at CERN

Giuseppe Ruggiero SNS & INFN, Pisa

“Kaon 2007”Frascati, 25/05/2007


The K decays: a theoretical clean environment sensitive to

new physicsFCNC loop processes: sd coupling and highest CKM suppression

Very clean theoretically: SD contributions dominate, hadronic matrix element can be related to measured quantites.

SM predictions (uncertainties from CKM elements): BR(K++) (1.6×10-5)|Vcb|4[2+(c-)2] (8.0 ± 1.1)×10-11

BR(KL0) (7.6×10-5)|Vcb|42 ± 0.6×10-11

Sensitive to NP: clean probe up to ~100 TeV scale


Effects of new physics on K decays F. Mescia

CKM 2006


Setting the bar for future K experiments

P3

26

P3

26 100 100

eventseventsMean:

E787/949

E787/949BR(K+) = 1.47

×1010

+1.30-0.89

SM

F. MesciaCKM 2006


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

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

Potosi, Sofia, Triumf, Turin

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

September 2005: presented at CERN SPSCDecember 2005: R&D endorsed by CERN Research BoardStart of the Gigatracker projectStart of test beams at CERN in 20062007: prototypes construction and test beams at CERN and Frascati2008 – 2010: Technical design and constructionStart of data taking 2011

Schedule

Located in the same hall of NA48


NA48/3 guidance principlesO(100) K++events ~ 10% background

2 Enemies

1) Physics: BR(SM) = 8×10-11

Acceptance 10%K decays ~1013

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

Kinematical rejection

Veto and particle ID

Kaon 3-momentum: beam trackerPion 3-momentum: spectrometer / detection: calorimetersCharged veto: spectrometer//e separation: RICH

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

Be pragmatic

KK+

m2miss=(PKP)2


Kinematics and Backgrounds

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


The experimental layout

+

10-6 mbar


The Beam

p

DECAYDECAY VOLUME VOLUME (~100 m)(~100 m)

K+ decay rate:

~11 MHz

P proton = 400 GeV/cProton/pulse 3.3×1012 (×3.3 NA48/2)Duty cycle 4.8/16.8 s

Primary beam

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

Secondary beam

Vertical view


The tracking system

6 chambers with 4 double layers of straw tubes each

Low X/X0 not to spoil the beam

Good space resolution not to spoil the downstream tracker resolution

200 Si m sensor + 100 Si m chip

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

(

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

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

Low X/X0

Good space resolution

Redundant p measurementVeto for charged particles

130 m per hit

2 magnets

The Gigatracker (i.e. the beam tracker)

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

Rate: 760 MHz (charged particles) ~50MHz/cm2

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

In vacuum, X/X0~0.1% per view

5 cm radius beam hole displaced in the bending plane

8.8

m

7.2

m

2.1

m

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


The particle ID system

CEDAR: existing Cerenkov counter at CERN to places on the beam Tag the kaon to keep the beam background under controlMinimal material budgetGood time resolution

H2 instead of NeNew phototubes

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

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

Time resolution 100 ps (track timing)

Velocity spectrometer (redundancy)

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

Phototubes with very good (t)

The CEDAR (i.e. the kaon ID)

The RICH (i.e. the pion ID)


The Veto system Large angle (10, 50 mrad): Rings calorimeters (in vacuum)

Rate: ~4.5 MHz () + ~0.5 MHz () (OR 12) 10-4 inefficiency for E in 0.05,1 GeV10-5 inefficiency for E>1 GeV

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

Rate: ~8.7 MHz ()+~4 MHz () )+~3 MHz ()10-4 inefficiency for E in 1,5 GeV10-5 inefficiency for E>5 GeV

Small angle (<1 mrad): Shashlik technologyRate: 0.5 MHz ()10-5 inefficiency (high energy photons)

New Readout

Extruded scintillator – lead sampling calorimeter 6 m long + magnet for beam deflectionRate: ~7 MHz ()+~3 MHz ()

10-5 inefficiency for detection

Deviate 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


Preliminary 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


Analysis: background rejectionEvents/year Total Region I Region II

Signal (acc=17%) 65 16 49

K++0 2.7 1.7 1.0

K++ 1.2 1.1 <0.1

K+e++ ~2 negligible ~2

Other 3 – track decays

~1 negligible ~1

K++0 1.3 negligible 1.3

K++ 0.5 0.2 0.2

K+e+(+)0, others

negligible

Total bckg. 9 3.0 6 S/B ~ 8 (Region I ~5,

Region II ~9)


Gigatracker: R&D programReadout chip: 1st MPW submission in

0.13mSubmitted in February 07Analogue FE blocks for the "CFD" option (Torino)FE amplifier discriminator NINO, LVDS driver (CERN)Wafers delivery ≈ end May 07ASICs characterization (t resolution, jitter, time walk)Tests card in progress (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

Irradiated test diode

itc-IRST wafer, 200µm

Si diode characterization with pulsed IR laser system

Towards a Technical ProposalTowards a Technical Proposal


Spectrometer: R&D programChosen technology: tube of mylar (25 m, D=1 cm, L=2.1 m)

100 straws produced in DubnaTests on gas leakageTests on tube expansion in vacuum Prototype assembled & cosmic ray tests October 2007: Prototype integration in NA48 set-up and test on beam


CEDAR: R&D program

CEDAR W-type filled with Ne tested at CERN in November 2006, using a 100 GeV hadron beam with 105 – 107 ppp (CERN, Firenze, Perugia).Test of fast photomultipliers using Cerenkov light.

CEDAR upgrade program

Beam Composition

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

1650 1700 1750 1800 1850 1900 1950 2000 2050

Pressure

%pion

kaon

proton


RICH: R&D programDesign, construction and test of a RICH prototype (CERN, Firenze, Perugia)Full length prototype (17 m, 0.6 m diamater, stainless steel tube at CERN)Mirror built, delivered and under test in FirenzeEndcap with 96 Hamatsu PMs readout through Winston’s conesPMs tested at SPS (2006) and Firenze (with laser)

Measured FWHM per single per phototube: 390ps (150 ps electronics and 110 ps laser included)

p

K

+

Simulatio

n

FWHM 0.375 ps

t ns

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


Large angle photon vetoes: R&D programKLOE-type lead/scintillating fiber: prototype constructed in

Frascati1 mm diameter scintillating fibers, 0.5 mm thick lead foils.

Readout granularity: 18 cellsVery well known and tested technologyUnder 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 built with this technology availableFermilab prototype under test at BTF

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

Lead scintillators tilesAijimura et al. NIM in press


Large angle photon vetoes: R&D program

ee

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

e- beam (300-500 MeV/c)Both calorimeter prototypes under test1st step: test with electrons2nd step: test with photons

Test beam periods in March, April, June 2007

Work carried on up to now using electrons:Understanding the beam backgroundCalibration of the prototypesFirst data analysis (efficiency, energy and time resolution)


Measurement of the inefficiencyK+ data taken in a dedicated NA48 test run in 2004 using K++0

LKr calorimeter: R&D program

Tagged using an SPS electron beam (2006)

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

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

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


Trigger

Level L0 “hardware” L1-L2 “software”

Input ~10 MHz 1 MHz

Output 1 MHz O(KHz)

Implementation

Dedicated hardware

TDAQ farm

Actions RICH minimum multiplicity, Muon

vetoing, LKr vetoing

L1 = single sub-detectorsL2 = whole event

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

A possible scheme:


Other physics opportunitiesP-326 Kaon Flux ~100 times NA48/2 Kaon

Flux

Other physics opportunities can be addressed:

Lepton – flavor violation: Ke2/K2,K+++e-, K+-+e+

Tests of CPT K++-e+

Search for new low mass particles: K+(light RH neutrinos) K++0P (pseudoscalar sGoldstino)

Hadron spetroscopy

…


ConclusionsNear future: Search for new physics using rare Kaon decays.

P-326 experiment: Measurement of the Br(K++) with a ~10% accuracy (+ other physics opportunities)

General design: Mostly defined. Overall simulation and performances under review.

R&D program: Well advanced: construction of detector prototypes and test in progress (in some cases completed). Important results by the end of 2007.

We propose a new experiment able to reach a ~10-12 sensitivity per event at an existing machine and employing the infrastructures of an existing experiment. [CERN-SPSC-P-326, 11/06/2005]

25/5/2007giuseppe ruggiero, kaon 20071 the k + + experiment at cern giuseppe ruggiero sns &...

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pisa kaon

s primary beam p kaon

kaon decays year

particle id kaon

mbar slide

p proton

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cern sps p326 cern