future of rare kaon decays at the cern-sps
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Future of Rare Kaon Decays at the CERN-SPS. Fermilab, October 7 , 2004 Ceccucci for the NA48-Future Working Group. “CERN Director General Outlines Seven-point Strategy for European Laboratory”. - PowerPoint PPT PresentationTRANSCRIPT
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October 7, 2004 A. Ceccucci/ CERN 1
Future of Rare Kaon Decays at the CERN-SPS
Fermilab, October 7 , 2004
A. Ceccucci for the
NA48-Future Working Group
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October 7, 2004 A. Ceccucci/ CERN 2
“CERN Director General Outlines Seven-point Strategy for European Laboratory”
18.6.2004 Official CERN Press Release Geneva 18 June 2004. At the 128th session of CERN Council, held today under the chairmanship of Professor Enzo Iarocci, CERN Director General, Robert Aymar, outlined a seven-point scientific strategy for the Organization. Top of the list was completion of the Large Hadron Collider (LHC) project with start-up on schedule in 2007. This was followed by consolidation of existing infrastructure at CERN to guarantee reliable operation of the LHC, with the third priority being an examination of a possible future experimental programme apart from the LHC.………
……….
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October 7, 2004 A. Ceccucci/ CERN 3
NA48 Data Taking
1997
1998
1999
2000
2001
2002
2003
NA48: ’/’/’/
’/ lower inst. intensity
NA48/1 KS
NA48/1: KS
KL
no spectrometer
NA48/2: K
1996Total: 5.3M KL00
2004NA48/2: K
Re ’/= 14.7 ± 2.2 10-4
First observation ofK0
S →0 ee and K0S →0
Ave: Re ’/= 16.7 ± 2.3 10-4
+ KL Rare Decays
Search for Direct CP-Violation in charged kaon decays
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October 7, 2004 A. Ceccucci/ CERN 4
NA48-Future Working Group
• We identified the Rare Kaon Decays as the next logical step of the Kaon Programme at CERN
• Short term (2004-2010):NA48/3 K+ → + LETTER OF INTENT
• Longer term (>2010):– Assuming a new or refurbished SPS capable to deliver higher
intensity/energy as the ultimate injector for LHC NA48/4 KL → 0 ee () NA48/5 KL → 0
CERN-SPSC-2004-010SPSC-EOI-002
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October 7, 2004 A. Ceccucci/ CERN 5
Letter of Intent to Measure the Rare Decay K → at the CERN SPS
Cambridge: D. Munday; CERN: N. Cabibbo, A. Ceccucci*, V. Falaleev, F. Formenti, B. Hallgren, A. Gonidec, P. Jarron, M. Losasso, A. Norton, P. Riedler G. Stefanini;Dubna: S. Balev, S. Bazylev, P. Frabetti, E. Goudzovski, D. Gurev,V. Kekelidze, D.
Madigozhin, N. Molokanova, R. Pismennyy, Y. Potrebenikov, A. Zinchenko; Ferrara: W. Baldini, A. Cotta Ramusino, P. Dalpiaz, C. Damiani, M. Fiorini,
A. Gianoli, M. Martini, F. Petrucci, M. Savrie’, M. Scarpa, H. Wahl; Firenze: E. Iacopini, M. Lenti, G. Ruggiero; Mainz: K. Kleinknecht, B. Renk, R. Wanke; UC Merced: R. Winston; Perugia: P. Cenci, M. Piccini; Pisa: A. Bigi, R. Casali, G. Collazuol, F.
Costantini, L. Di Lella, N.Doble, R. Fantechi, S.Giudici, I. Mannelli, A. Michetti, G.M. Pierazzini, M. Sozzi; Saclay: B. Peyaud, J. Derre; Sofia: V. Kozhuharov, L.Litov, S.
Stoynev; Torino: C. Biino, F. Marchetto
*contact person
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October 7, 2004 A. Ceccucci/ CERN 6
Main K+ decay modes competing with K+→+
Decay
e
BR63 % 21 % 6 % 2 % 3 % (called K+
3) 5 % (called K+
e3)
Suppression:PID, kinematics veto, kinematicsCHV, kinematics veto, kinematics veto, PID veto, E/P
BR(K+→+ )~10-10 !!
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October 7, 2004 A. Ceccucci/ CERN 7
Framework• So far K+→+ only studied with kaon decays at rest
– This limits the statistics to a few events• We plan to collect ~100 events at the SPS by 2010
– We dubbed this initiative NA48/3 – the name is not an issue at this early stage
• Employ high energy kaons has the following advantages:– The larger cross section increases the kaon content in the beam– The rejection of backgrounds from K→ is simplified
• Tens of GeV of EM energy is deposited in the photon vetoes!– Accidental background are minimised
• The use of unseparated beam becomes a possibility• 2/3 of the final state is invisible !!
– The kaon and the pion must be redundantly measured to keep backgrounds under control
– Muon and photon vetoes are essential
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October 7, 2004 A. Ceccucci/ CERN 8
Kinematics75 /KP GeV c
K
0K
Region I
K
Region II
K
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October 7, 2004 A. Ceccucci/ CERN 9
Acceptance
75 / 40 /Acceptance (Region I+II) ~ %KP GeV c P GeV c
( / )KP GeV c ( / )KP GeV c
Acc
epta
nce
Acc
epta
nce
Region I Region II2 2 20 0.01 ( / )missm GeV c 2 2 20.026 0.068 ( / )missm GeV c
14 ( / ) 40P GeV c 14 ( / )P GeV c
14 ( / ) 30P GeV c
75 GeV/c
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October 7, 2004 A. Ceccucci/ CERN 10
THE BEAM
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October 7, 2004 A. Ceccucci/ CERN 11
Rationale p0 = primary proton momentum pk = secondary beam momentum
• Kaon production increases as p02
– Use highest p0 (that is 400 GeV/c protons from SPS)• For a fixed fiducial length the number of decays
increases as pk. If p0 is fixed the maximum is for:
pk = 0.23 p0 • For unseparated beams the limitation comes from
the detectors, not from the amount of protons
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October 7, 2004 A. Ceccucci/ CERN 12
Choice of pk=75 GeV/c
Pk (GeV/c
60 75 90 120K+ flux @ production( 3 1012 400 GeV/c protons)
x108 1.11.3 (meas)
1.5 1.9 2.42.3 (meas)
K+ survival over 102 m 0.80 0.83 0.86 0.89K+ / Total beam rate x10-2 5.2
6.8 (meas)5.5 5.6 5.2
4.7 (meas)K+ decays in 50 m x106 8.9 10.7 11.6 11.4
75 GeV/c is about the maximum momentum for which a beam incorporatingstages for large solid angle acceptance, momentum selection, K+ tagging, beam momentum measurement and tracking using standard beam elements can fit into the present length of 102 m
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October 7, 2004 A. Ceccucci/ CERN 13
NA48/3: Beam Layout
Beam-line 102 m long
about 17%K+ lost
DipolesDipoles
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October 7, 2004 A. Ceccucci/ CERN 14
NA48/3: Beam Across Tank
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October 7, 2004 A. Ceccucci/ CERN 15
Beam:Present K12
(NA48/2)New HI K+
> 2006Factor
wrt 2004SPS protons per pulse on T10 1 x 1012 3 x 1012 3.0Duty cycle (s./s.) 4.8 / 16.8 1.0Solid angle (sterad) 0.40 16 40Av. K+momentum <pK> (GeV/c)
60 75 Total : 1.35
Mom. band RMS: (p/p in %) 4 1 ~0.25Area at Gigatracker (cm2) 7.0 20 2.8Total beam per pulse (x 107) per Effective spill length (MHz) / … / cm2 (KABES) (MHz)
5.5182.5
25080040
~45 (~27)~45 (~27)~16 (~10)
Eff. running time / yr (pulses)
3* x 105 3.1 * 105 1.0
K+ decays per year 1.0x1011 4.0x1012 40
New high-intensity K+ beam for NA48/3 AlreadyAvailable
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October 7, 2004 A. Ceccucci/ CERN 16
TURTLE SIMULATIONMOMENTUM DISTRIBUTION
1HISTOGRAM NO 21 DISTRIBUTION OF P IN GEVC 102.000 M FROM THE TARGET0 INTERVAL SCALE FACTOR.. 100 X'S EQUAL 5637 ENTRIES0LESS THAN 72.000 0
72.000 TO 72.200 0 72.200 TO 72.400 0 72.400 TO 72.600 0 72.600 TO 72.800 0 72.800 TO 73.000 1 73.000 TO 73.200 20 73.200 TO 73.400 178 XXX 73.400 TO 73.600 576 XXXXXXXXXX 73.600 TO 73.800 1210 XXXXXXXXXXXXXXXXXXXXX 73.800 TO 74.000 2068 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.000 TO 74.200 2870 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.200 TO 74.400 3727 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.400 TO 74.600 4598 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.600 TO 74.800 5354 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 74.800 TO 75.000 5637 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.000 TO 75.200 5596 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.200 TO 75.400 5126 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.400 TO 75.600 4288 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.600 TO 75.800 3400 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 75.800 TO 76.000 2623 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 76.000 TO 76.200 1820 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 76.200 TO 76.400 1068 XXXXXXXXXXXXXXXXXX 76.400 TO 76.600 552 XXXXXXXXX 76.600 TO 76.800 250 XXXX 76.800 TO 77.000 61 X 77.000 TO 77.200 8 77.200 TO 77.400 0 77.400 TO 77.600 0 77.600 TO 77.800 0 77.800 TO 78.000 00GREATER THAN 78.000 00 TOTAL NUMBER OF ENTRIES = 51031 INCLUDING OVERFLOW AND UNDERFLOW0 MEAN = 74.981 RMS HALF WIDTH = 0.7100HISTOGRAM NO 21 DISTRIBUTION OF P IN GEVC 102.000 M FROM THE TARGET
<p> = 74.981 GeV/c, RMS = 0.710 GeV/c
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October 7, 2004 A. Ceccucci/ CERN 17
-60.000 -20.000 20.000 60.000 TOTALS I**---**---**---**---**---**---**I---------60.000 I I 0-54.000 I I 0-48.000 I I 0-42.000 I I 0-36.000 I I 0-30.000 I I 0-24.000 I 8T$$$$$$$$$A I 932-18.000 I A$$$$$$$$$$$$A I 5407-12.000 I Z$$$$$$$$$$$$Z I 8326 -6.000 I $$$$$$$$$$$$$$ I 9999 0.000 I $$$$$$$$$$$$$$ I 9999 6.000 I W$$$$$$$$$$$$W I 8536 12.000 I 4$$$$$$$$$$$$G I 5529 18.000 I 3Q$$$$$$$$T2 I 787 24.000 I I 0 30.000 I I 0 36.000 I I 0 42.000 I I 0 48.000 I I 0 54.000 I I 0 I**---**---**---**---**---**---**I-------- I I I 134455554431 I
I 15428485392461 I I 59077738177357 I TOTALS I 000000007855957371007700000000 I 9999
TOTAL NUMBER OF ENTRIES = 51031
-60.000 -20.000 20.000 60.000 TOTALS I**---**---**---**---**---**---**I---------60.000 I I 0-54.000 I I 0-48.000 I I 0-42.000 I I 0-36.000 I I 0-30.000 I I 0-24.000 I 4H$$$$$$$$K5 I 603-18.000 I 3$$$$$$$$$$$$ I 5010-12.000 I H$$$$$$$$$$$$K I 8414 -6.000 I H$$$$$$$$$$$$H I 9999 0.000 I L$$$$$$$$$$$$H I 9999 6.000 I A$$$$$$$$$$$$E I 8483 12.000 I $$$$$$$$$$$$6 I 5058 18.000 I 4L$$$$$$$$H3 I 590 24.000 I I 0 30.000 I I 0 36.000 I I 0 42.000 I I 0 48.000 I I 0 54.000 I I 0 I**---**---**---**---**---**---**I-------- I I I 134456555431 I I 213971951312 I I 61257420138277 I TOTALS I 000000008999158636733400000000 I 9999
TOTAL NUMBER OF ENTRIES = 51031
-60.000 -20.000 20.000 60.000 TOTALS I**---**---**---**---**---**---**I---------60.000 I I 0-54.000 I I 0-48.000 I I 0-42.000 I I 0-36.000 I I 0-30.000 I I 0-24.000 I 2AQ$$$$$$OF1 I 397-18.000 I $$$$$$$$$$$$ I 4016-12.000 I 1$$$$$$$$$$$$4 I 8053 -6.000 I 2$$$$$$$$$$$$2 I 9999 0.000 I 3$$$$$$$$$$$$2 I 9999 6.000 I $$$$$$$$$$$$ I 8186 12.000 I $$$$$$$$$$$$2 I 4102 18.000 I 2GS$$$$$$$F2 I 396 24.000 I I 0 30.000 I I 0 36.000 I I 0 42.000 I I 0 48.000 I I 0 54.000 I I 0 I**---**---**---**---**---**---**I-------- I I I 2456666542 I I 631337614046 I I 7435062357861 I TOTALS I 000000006682187334832000000000 I 9999
TOTAL NUMBER OF ENTRIES = 51031
SPIBES1
X [mm]
Y [mm]
SPIBES2
FTPC (KABES)
BEAM TRANSVERE SIZE
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October 7, 2004 A. Ceccucci/ CERN 18
1HISTOGRAM NO 29 HORIZONTAL AXIS X IN MM 204.858 M FROM THE TARGET VERTICAL AXIS Y IN MM 204.858 M FROM THE TARGET0 -60.000 -20.000 20.000 60.000+ TOTALS I**---**---**---**---**---**---**I-------- -60.000 TO -54.000 I I 0 -54.000 TO -48.000 I I 0 -48.000 TO -42.000 I I 0 -42.000 TO -36.000 I I 0 -36.000 TO -30.000 I 2321 11 I 10 -30.000 TO -24.000 I 159XT$$$$SJE73 I 334 -24.000 TO -18.000 I 8$$$$$$$$$$$U72 I 1947 -18.000 TO -12.000 I 1E$$$$$$$$$$$$D I 4900 -12.000 TO -6.000 I G$$$$$$$$$$$$J1 I 8143 -6.000 TO 0.000 I 1L$$$$$$$$$$$$I2 I 9999 0.000 TO 6.000 I G$$$$$$$$$$$$82 I 9984 6.000 TO 12.000 I G$$$$$$$$$$$$E1 I 8252 12.000 TO 18.000 I F$$$$$$$$$$$$E1 I 4901 18.000 TO 24.000 I AV$$$$$$$$$$X7 I 1929 24.000 TO 30.000 I 2ERYVWQSPFF5 I 254 30.000 TO 36.000 I 21 1 1 I 5 36.000 TO 42.000 I I 0 42.000 TO 48.000 I I 0 48.000 TO 54.000 I I 0 54.000 TO 60.000 I I 0 I**---**---**---**---**---**---**I-------- I I I 1356776531 I I 15731887723651 I I 16166042762880 I TOTALS I 000000027056033304565390000000 I 9999 0 TOTAL NUMBER OF ENTRIES = 51031 INCLUDING UNDERFLOW AND OVERFLOW AS FOLLOWS 0 UNDERFLOW OVERFLOW ACROSS 0 0 DOWN 0 0
0HISTOGRAM NO 29 HORIZONTAL AXIS X IN MM 204.858 M FROM THE TARGET VERTICAL AXIS Y IN MM 204.858 M FROM THE TARGET
Spot at Wire Chamber 6:
X [mm]
Y [mm]
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October 7, 2004 A. Ceccucci/ CERN 19
Muon Halo Calculation• The flux of “halo muons” crossing the
WC has been calculated using the HALO program:
• Single rate in the WC is dominated by muons from kaon decays
• The total halo is about 7 MHz• Thank to the new beam design, the
situation appears much better than in NA48/2
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October 7, 2004 A. Ceccucci/ CERN 20
DETECTORS
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October 7, 2004 A. Ceccucci/ CERN 21
NA48/3 Detector Layout
800 MHz(/K/p)
Only the upstream detectors see the 800 MHz beam
10 MHz Kaon decays
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October 7, 2004 A. Ceccucci/ CERN 22
Detectors• CEDAR
– To tag positive kaon identification• GIGATRACKER
– To Track secondary beam before it enters the decay region• ANTI
– Photon vetoes surrounding the decay tank • WC
– Wire chambers to track the kaon decay products• CHOD
– Fast hodoscope to make a tight K-pi time coincidence • LKR
– Forward photon veto and e.m. calorimeter• MAMUD
– Hadron calorimeter, muon veto and sweeping magnet• SAC and CHV
– Small angle photon and charged particle vetoes
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October 7, 2004 A. Ceccucci/ CERN 23
2004 Test beam• It was of the utmost importance to test in 2004 the performance
of the NA48 detectors at intensities comparable to NA48/3 (no SPS in 2005!)
• This was a unique opportunity to collect data to validate our –simulated- understanding to quantify the necessary effort (technical and financial) to transform NA48 into an experiment capable to address K+→+ .
• Thank to the extension granted by CERN we could test:– WC: raise intensity to about 30 times NA48/2– GIGATRACKER
• Tested a state-of the-art ALICE SPD assembly in our beam• Use a thinner 25 micron MICROMEGAS amplification gap• Read out KABES with 480 MHz FADC (former NA48 tagger FADC)• Read KABES at ~14 times the NA48/2 rate
– LKR: Complement the photon coverage with extra LKr electronics and a Small Angle Calorimeter SAC (CMS RCAL prototype)
– CHOD test of prototypes• A few very preliminary results will be shown
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October 7, 2004 A. Ceccucci/ CERN 24
Increase of beam Intensity• I0 = Intensity of NA48/2 K+ beam
– Tune the K12 beam to + 75 GeV/c – Open up the aperture of the P42 line (X3.5)– Opening momentum bite P/P from 5 to 20 % (X4)– Turn on both K+ and K- polarities (X1.3)– Employ a shorter T4 target (100 mm instead of 300
mm) (X1.6) • Tot ~ 29 I0• Accidentals in 29 I0 beam NA48/2 are
dominated by pions rather than kaons– Expect cleaner situation with new beam
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October 7, 2004 A. Ceccucci/ CERN 25
CEDAR• CErenkov Differential Counter with Achromatic
Ring Focus• He pressure adjusted to make it sensitive only to kaons• Requires beam divergency < 0.1 mrad • Built at CERN in the 80’s (Bovet et al.) for use in the SPS beam lines• We will certainly need to upgrade the photon detectors and front-end
electronicsto operate at the NA48/3 rates (~60 MHz)
Beam
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October 7, 2004 A. Ceccucci/ CERN 26
CEDAR2 21 2
22m m
p
K/
( / )p GeV c
Cedar-W
Cedar-N
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October 7, 2004 A. Ceccucci/ CERN 27
GIGATRACKER• Specifications:
– Momentum resolution to ~ 0.5 % – Angular resolution ~ 10 rad– Time resolution ~ 100 ps– Minimal material budget– Perform all of the above in
• 800 MHz hadron beam, 40 MHz / cm^2• Hybrid Detector:
– SPIBES (Fast Si micro-pixels)• Momentum measurement • Facilitate pattern recognition in subsequent FTPC• Time coincidence with CHOD
– FTPC (NA48/2 KABES technology with FADC r/o)• Track direction
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October 7, 2004 A. Ceccucci/ CERN Mara Martini 28
GIGATRACKERSP
IBE
S1
SPIB
ES2
FTPC
6.25 12.45 m
♠ momentum: use SP1 and SP2 to measure y = 40 mm displacement. Assuming σp~50µm from pixel and 350µm thick Si (0.37% X0)
σ = (σp√2 ‡ σMS ) ⁄ 40 mm = 0.25%
♠ direction: use SP2 and FTPC. Assuming σp~100µm from pixel and similar from FTPC and no MS from FTPC (from SP2 no influence)
∆Өх= σp√2 ⁄ 12.4m = 11µrad
Tails in the beam? (Turtle simulation)
♠ time resolution: essential to obtain a low background due to accidental hits and to allow the pattern recognition (see result from test beam) . For a pixel C≈ 100 fF a risetime ~ 2 ns should be achievable for 130 nm technology and a good S/N.
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October 7, 2004 A. Ceccucci/ CERN Mara Martini 29
Proposal for SPIBES
5 cm
300 x 100 µm pixel cell 80000 pixels in total to cover the beam
• An effort must be done to minimize the overall thickness to ≤ 350 µm of Si without loosing in yield .
• Should avoid a substrate
• The cooling should be studied
• The dimension of the pixel cell and of the chip must be optimized to fit the 2n rule and to match the design requirements (PA, Discri, multiplexed TDC, power consumption, r/o bus)
Beam square shape 5x5 cm2
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October 7, 2004 A. Ceccucci/ CERN 30
Test of ALICE pixel in NA48/2 beam 1 ALICE assembly
1 DAQ adapter card 30 m DAQ cables
30 m JTAG control cables LV and HV power supplies
VME crate with r.o. module (Pilot) and JTAG
controller JTAG multiplexer
MXI interface to PC ALICE PTS software
(LabView)
PC remotely controlled from NA48 control room
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October 7, 2004 A. Ceccucci/ CERN 31
Single Chip Alice Assembly tested
Assembly 7:•150µm thick ALICE chip•200µm thick sensor• 1.1 % X0 all together
Mounted on a thin test-PCB
Vfd=15VVop=50V
8192 pixelsProduced 2003, tested inALICE p-TB 2003
Sensor
Chip
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October 7, 2004 A. Ceccucci/ CERN 32
MULTIPLICITY (200 nsec gate)
I0I0/4
4xI0
14xI0
<mult> = 1.1 <mult> = 1.3
<mult> = 3.1 <mult> = 7.8
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October 7, 2004 A. Ceccucci/ CERN 33
MULTIPLICITY (200 nsec gate)MULTIPLICITY (200 nsec gate)
for r/o window of 10 ns:
1GHz x 10 ns x 1.1 ~ 10 hits/ trig
for σ = 100ps we expect in a ±2.5σ:0.5 accident hits/trig
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October 7, 2004 A. Ceccucci/ CERN 34
FTPC (KABES+FADC)• NA48/2
– KABES has achieved very good performance – Position resolution ~ 70 micron– Time resolution ~ 0.6 ns– Rate per micro-strip ~ 2 MHz
• NA48/3 – Intensity ~ 10 higher per unit area– 600 ns drift – The long drift (600 ns) makes a standalone pattern
recognition very difficult or just impossible ( That’s why we plan to have SPIBES in front)
– To reduce double pulse resolution and improve the time resolution one has to reduce the pulse duration and possibly read-out every micro-strip with 1 GHz FADC
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October 7, 2004 A. Ceccucci/ CERN 35
driftE
driftETdrift1
Tdrift2
Operated @ Edrift=0.83kV/cm
Tdrift1 + Tdrift2 = 750ns
48 strips with 0.8 mm pitch
Very low discharge probability
MicromegasGap 50 μm
MicromegasGap 50 μm
KABES principle: TPC + micromegas
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October 7, 2004 A. Ceccucci/ CERN 36
TEST OF KABES IN 2004LOW INTENSITY
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October 7, 2004 A. Ceccucci/ CERN 37
Recent lab test with 25 m gap
50 m gap 25 m gap improvement of occupancy observed with 25m amplification
gap
Width ~30 ns Width ~18 ns
KABES 25 micron amplification gap
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October 7, 2004 A. Ceccucci/ CERN 38
BEAM DATA: 50/25μ mesh 2003/2004
Time over Threshold (ns)
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October 7, 2004 A. Ceccucci/ CERN 39
2004 KABES TEST HIGH INTENSITY FLUX PER UNIT AREA CLOSE TO NA48/3 !
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October 7, 2004 A. Ceccucci/ CERN 40
TEST OF KABES with 480 MHz FADC
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October 7, 2004 A. Ceccucci/ CERN 41
FADC Readout (1)• 8 bit FADC 960 MHz (2 interleaved 480 MHz) from NA48 proton tagger• 9 FADC boards (18 channels “480 MHz mode”)• 18 FADC channels connected to KABES strips
in station upstream UP and downstreamK1 23 FADC 16K1 24 FADC 14K1 25 FADC 12K1 26 FADC 10
K2 23 FADC 6K2 24 FADC 4K2 25 FADC 2K2 26 FADC 18
K5 23 FADC 1K5 24 FADC 8K5 25 FADC 3K5 26 FADC 5K5 27 FADC 7
K6 23 FADC 9K6 24 FADC 11K6 25 FADC 13K6 26 FADC 15K6 27 FADC 17
K2K1
K3 K4
K5 K6
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October 7, 2004 A. Ceccucci/ CERN 42
Multiple pulses without Zero-suppression
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October 7, 2004 A. Ceccucci/ CERN 43
FADC data (1)
• Distribution of time over threshold– Low intensity run– Threshold set to 37 ADC
counts (~27 mV)– ±2 samples over
threshold
~20 ns time over threshold(KABES 25 µm mesh)
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October 7, 2004 A. Ceccucci/ CERN 44
FADC data
x1 x3
x7 x12
• Number of pulses per channel as a function of beam intensity
– noisy channels 10,12,14,16 all connected to K1
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October 7, 2004 A. Ceccucci/ CERN 45
Multiple pulses with Zero-supp
• Some data from RUN 16964 (14xI0)
• horizontal scale: FADC time units (2×1.04 ns)
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October 7, 2004 A. Ceccucci/ CERN 46
Attempt to fit single pulses
23
22
2241 1 P
Pt
ePtPP
• fit of 500 FADC pulses from the low intensity RUN (16916)
• 4 parameters function used:
• uncertainty of 1.7 counts per FADC value
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October 7, 2004 A. Ceccucci/ CERN 47
Attempt to fit multiple pulses
• “hand fit” of a six pulses event from run 16964 (x 14 I0)
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October 7, 2004 A. Ceccucci/ CERN 48
KABES FADC Conclusion• We read-out the micro-strips with FADC• Double pulse resolution capability is
very good• To do list:
– develop reconstruction from list of times in strips and measure resolution (space, time, angular) as a function of beam intensity
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October 7, 2004 A. Ceccucci/ CERN 49
ANTI• Set of ring-shaped photon vetoes surrounding the
decay tank• Specification: inefficiency to detect photons above
100 MeV < 10-4
• The NA48 ANTI’s (AKL) need to be replaced• Extensive R&D Performed by American and
Japanese groups • Claims that inefficiency as low as 10-5 can be
achieved• Baseline solution: Lead/ Plastic scintillator sandwich
(1-2 mm lead / 5 mm plastic scintillator)• Cost driver of NA48/3
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October 7, 2004 A. Ceccucci/ CERN 50
Current NA48 ANTI
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October 7, 2004 A. Ceccucci/ CERN 51
WIRE CHAMBERS
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October 7, 2004 A. Ceccucci/ CERN 52
NA48 WC
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October 7, 2004 A. Ceccucci/ CERN 53
Beam Test 2004: WC
• With the exception of one sector in the Y view of DCH3 all other channels could be operated at nominal HV at the highest beam intensity
• Quite encouraging: plane efficiency decreases only by 1-2% • Ability to operate the WC at intensity close to NA48/3 cannot be
overemphasised !!
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October 7, 2004 A. Ceccucci/ CERN 54
WC @ 30 x I0
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October 7, 2004 A. Ceccucci/ CERN 55
WC: Kinematical rejection
Events accepted
( / )P GeV c
2 2 2( / )missm GeV c0
Region I
Region I
2 2 2 2( cos )miss K K K Km EE pm m p Measured quantities
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October 7, 2004 A. Ceccucci/ CERN 56
Double spectrometer layoutDCH1DCH1 DCH2DCH2 DCH3DCH3 DCH4DCH4 DCH5DCH5 DCH6DCH6KevlarKevlar Mag1Mag1 Mag2Mag2
zz
xx
VacuumVacuum HeHe
NA48 Wire chambers 0.004 XNA48 Wire chambers 0.004 X00KevlarKevlar
zz
xx
VacuumVacuum HeHe
NA48 Wire chambers 0.004 XNA48 Wire chambers 0.004 X00Straw tube 0.0025 XStraw tube 0.0025 X00
kickT 211 /P MeV c
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October 7, 2004 A. Ceccucci/ CERN 57
Double spectrometerTwo independent measurement of P
DCH1 invacuum
Single configuration
Doubleconfiguration
Simulation with gaussian MS
0
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October 7, 2004 A. Ceccucci/ CERN 58
WC (baseline solution) • NA48/2
– Four larger drift chambers and one large-gap dipole magnet (MNP33/1)
– The Read out of the chambers is modern (2002)– Chambers enclosed in He by thin (0.3 %) Kevlar membrane
• NA48/3 – Add two chambers and one copy of MNP/33– Consider first tracking station operated in vacuum to
improve the angular resolution (and missing mass)– For this we are evaluating the ATLAS/COMPASS Straw
technology– Straws have been employed in high rate rare kaon decays
experiment (AGS-E871, KL→e) with rates as high as 750 KHz/wire
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October 7, 2004 A. Ceccucci/ CERN 59
Can we do w/o beampipe?
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October 7, 2004 A. Ceccucci/ CERN 60
WC (More elegant solution)• Replace all WC with straws and extend the
vacuum down to the CHOD (original CKM idea)
• This would allow to remove the beam-pipe, thus simplify the scheme to render hermetic the photon vetoes in the intermediate region between the LKR and SAC3 at the end of the hall
• This solution will likely reduce the number of e.m. showers generated in the beam-pipe.
• These showers may lead to a non-negligible load on the chambers and read-out
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October 7, 2004 A. Ceccucci/ CERN 61
CHOD• It is used to provide a fast trigger and
(together with the gigatracker) to provide the time coincidence to associate the “right” kaon track to the pion track
• Investigating three solutions:– Scintillator tiles– Fused silica to use cherenkov light– Multi-gap glass RPC (ALICE).
• Excellent time resolution (< 50 ps) for rates up to 1 KHz/cm^2
• But in the hottest regions near the beam pipe of NA48/3, rates up to 5 KHz/cm^ have been measured further studies needed
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October 7, 2004 A. Ceccucci/ CERN 62
LKR• The NA48 Liquid Krypton Calorimeter • Must achieve inefficiency < 10-5 to detect photons
above 1 GeV • Advantages:
– It exists – Homogeneous (not sampling) ionization calorimeter– Very good granularity (~2 2 cm2)– Fast read-out (Initial current, FWHM~70 ns)– Very good energy (~1%, time ~ 300ps and position (~1 mm)
resolution• Disadvantages
– 0.5 % X0 of passive material in front of active LKR– The cryogenic control system needs to be updated
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October 7, 2004 A. Ceccucci/ CERN 63
NA48 Liquid Krypton Calorimeter
9 m3 of L kr (1 32 12 cell s)
1. 25 m de ph (27 X
0 )
(E)/E = 3.2%/E 9 % /E 0.42%(m)~1 MeV/c2 ;(t) ~ 300 ps
FAST: 70 ns FWHM (it can be reduced)EXCELLENT GRABULARITY: 2 2 cm2
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October 7, 2004 A. Ceccucci/ CERN 64
2004 TEST OF LKR AS PHOTON VETO
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October 7, 2004 A. Ceccucci/ CERN 65
LKR Hermeticity• According to simulation we should be able to
address 0 rejection inefficiency to 10-5-10-6 complementing the NA48/2 setup with:– A SAC and the end of the hole– Read out the corner of LKR which are usually not
read out• We have prepared the above for the beam
test in 2004• Since we currently we have no beam
sweeper, intensity of beam was reduced to 1/6 of NA48/2 nominal: test of hermeticity at low intensity.
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October 7, 2004 A. Ceccucci/ CERN 66
Small angle photon vetoPbWO4 crystals (CMS) Dimension of crystals 2x2x23 cm3 7 x 7 cm matrix ~ 25 X0 Readout with light guides and PMTInstalled for last week of data taking
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October 7, 2004 A. Ceccucci/ CERN 67
Full LKr read-outInstalled for last weekInstalled for last week
of data taking of data taking New instrumentedNew instrumented
LKr regions work.LKr regions work.
XLKr (cm)
YLKr (cm)
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October 7, 2004 A. Ceccucci/ CERN 68
General definitions
2 2 2( / )missm GeV c
Region I
Region II
( / )P GeV c
K
0
0 Peak Region
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October 7, 2004 A. Ceccucci/ CERN 69
How to measure +0 Rejection
M2(miss) (GeV/c2)2 M2(miss) (GeV/c2)2
DATAMC
DATAMC
745862 MC212569 DATA
1486 MC678 DATA
0 peak BEFORE APPLICATION OF EXTRA CLUSTERS IN LKR
AFTER APPLICATION OF EXTRA CLUSTERS IN LKR
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October 7, 2004 A. Ceccucci/ CERN 70
LKR: Work in progress...
• Detectors:– Read-out for LKr corners work– Must understand effect of e.m. showers initiated in
ANTI and Beam pipe spilling into WC on tight one track trigger (underestimate the photon rejection)
– SAC works; must improve reconstruction– Collected several millions of unbiased →
• These data are invaluable to compare with our assumptions and to design the new experiment
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October 7, 2004 A. Ceccucci/ CERN 71
MAMUD• To provide pion/muon separation and beam
sweeping. – Iron is subdivided in 150 2 cm thick plates (260 260 cm2 )
• Four coils magnetise the iron plates to provide a 1.3 T dipole field in the beam region• Active detector:
– Strips of extruded polystyrene scintillator (1 x 4 x130 cm3) – Light is collected by WLS fibres 1.2 mm diameter
• As shown by our Fermilab CKM friends, if backgrounds from K→ remains a concern, a tracking RICH in place of the second magnetic spectrometer would completely remove it
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October 7, 2004 A. Ceccucci/ CERN 72
MAMUD rough parameters (MARCELLO
LOSASSO)Total weight ≈ 150 ton
Overall Dimension 2.6 m x 2.8 m x 5.25 m (WxHxL)
Number of iron plates (2x) 150
Current ≈ 4 KA
Power ≈ 0.8 MW
Field integral on axis (from -5 m to +5 m) 6.85 T m
Magnetic field into a “good field region” (by 10 cm x 10 cm)
≈ 1.3 T
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October 7, 2004 A. Ceccucci/ CERN 73
Proposed Dipole configuration
Pole gap is 11 cm V x 30 cm H
Coils cross section 15cm x 25cm
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October 7, 2004 A. Ceccucci/ CERN 74
Main results of simulation
Magnetic field at z=0 m
Field integral on axe
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October 7, 2004 A. Ceccucci/ CERN 75
NA48/3 Organisational Matters
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October 7, 2004 A. Ceccucci/ CERN 76
Time Schedule• 2004
– Launch GIGATRACKER R&D– Vacuum tests– Evaluate straw tracker– Start realistic cost estimation– Complete analysis of beam-test data
• 2005– Complete of the above– Complete Specifications– Submit proposal to SPSC
• 2006-2008– Costruction, Installation and beam-tests
• 2009-2010– Data Taking
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October 7, 2004 A. Ceccucci/ CERN 77
Conclusions• We have found a fortunate combination
where a compelling physics case can be addressed with an existing accelerator, employing the infrastructure (i.e. civil engineering, hardware, some sub-systems) of an existing experiment
• We stress that this initiative in not a mere continuation of NA48
• The working group has now becoming a proto-collaboration seeking the qualified participation of new collaborators
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October 7, 2004 A. Ceccucci/ CERN 78
*Breaking News*• John Dainton, CERN SPSC Chairman,
released this morning the conclusions of the “Villars” meeting on the Future of Fixed Target Programme at CERN during a CERN Particle Physics Seminar
• The SPSC supports our R&D and looks forward to receive the Proposal
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October 7, 2004 A. Ceccucci/ CERN 79
Kaons: Longer term (i.e. More Protons Needed!)
• K0L→ 0eeand K0
L→ 0(NA48/4)• K0
L → 0 (NA48/5)
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October 7, 2004 A. Ceccucci/ CERN 80
0++, 2++
Direct CPV
Indirect CPV
CPC
K0L→0ee and K0
L→0
Study Direct CP-Violation
•Indirect CP-Violating Contribution has been measured (NA48/1, see next slide)•Constructive Interference (theory)•CP-Conserving Contributions are negligible
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October 7, 2004 A. Ceccucci/ CERN 81
K0S →0 ee and K0
S →0
KS →0 eeKS →0
BR(KS→0ee) 10-9 = 5.8 +2.8
-2.3(stat) ± 0.8(syst)
|as|=1.06+0.26-0.21 (stat) ± 0.07 (syst)
PLB 576 (2003)
7 events, expected back. 0.15
BR(KS→0) 10-9 = 2.9 +1.4
-1.2(stat) ± 0.2(syst)
|as|=1.55+0.38-0.32 (stat) ± 0.05 (syst)
La Thuile, Moriond 2004
6 events, expected back. 0.22
NA48/1 NA48/1
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October 7, 2004 A. Ceccucci/ CERN 82
K0L→ee() : Perspectives
• Detector ×2 – Very ambitious, KTeV/NA48 already state of the art
• KS-KL time dependent interference ×2– Position experiment between 9 and 16 KS lifetimes (hep-ph/0107046)
• KS-KL time independent interference ×3 – Assume constructive interference (theoretically preferred)
• Data Taking ×5 – Run in “factory mode”. After all E799-II run only for a few months to
collect ~7 × 1011 KL decays• Beam intensity ×4
– Need ~1012 protons/sec, slowly extracted, high energy (≤ 1 TeV), DC • Tot ~ ×240 → sens on BR ~ ×15 (on Im t ~×4-15)
– explore the window of opportunity between current upper limit and SM
Ideal Kaon Application for High Intensity/High Energy Machine
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October 7, 2004 A. Ceccucci/ CERN 83
KL→0@CERN?
NA48/5?
E391A
J-PARC
CERN may become competitive if the E391A technique works
From KAMI proposal
SPS
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October 7, 2004 A. Ceccucci/ CERN 84
Conclusions
– A competitive programme can start pnow for charged kaons at the current SPS
– For a very competitive neutral kaon decay experiment, ~ 1013 slowly extracted, high energy protons per second would be needed
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October 7, 2004 A. Ceccucci/ CERN 85
SPARES
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October 7, 2004 A. Ceccucci/ CERN 86
Comparing Apples with ApplesNA48/3 P940
Accelerator CERN-SPS FNAL-MI
Energy (GeV) 400 120
Duty cycle (s /s ) 4.8 / 16.8 = 0.29 1.0 / 3.0 = 0.33
1 HEP year (s) 107 107
Eff. Spill. Length (s / s) 3.0 / 4.8 = 0.63 1.0 / 1.0 (?)
Total Rate (GHz) 0.8 0.23
Fraction of Kaons (%) 6 4
Flux of Kaons (MHz) 50 10
Decay fraction (%) 9 (50 m / 100 m) 17 (60 m / 67 m)
Acceptance (%) 10 5
Events/y (BR~10-10) 82 31
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October 7, 2004 A. Ceccucci/ CERN 87
Optics drawing :
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October 7, 2004 A. Ceccucci/ CERN 88
Compatibility/Competition• NA48/3 is fully compatible with COMPASS running
– We need only 3 1012 per cycle (already available now on T4!)• There are two approved competitors for beam time
– LHC filling and CNGS• The extent of the project implies that there should
not be in addition (at the stage of data taking)– A fixed target heavy ion programme– Any other experiment in ECN3 competing for proton beam
time• We understand that the SPS can deliver protons for
fixed target physics even when LHC is being operated with ions
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October 7, 2004 A. Ceccucci/ CERN 89
Detector Layout
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October 7, 2004 A. Ceccucci/ CERN 90
0 20 40 60 80 1000
10
20
30
40
50Pr
oduc
tion
ratio
Kaon momentum (GeV/c)
Ratio of K+ production at 400 and 120 GeV/c
By LAU GATIGNONCERN/AB
0 vetoing is easierfor high energy kaons, it pays off to go to highest proton energy!!
The CERN-SPS is the best machine
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October 7, 2004 A. Ceccucci/ CERN 91
ALICE PIXEL IN NA48 BEAM
Giorgio StefaniniFadmar OsmicDOCT
Petra Riedler Alex Kluge Michel MorelMike BurnsPeter Chochula
ALICE pixel team members helping with the preparations and the test:
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October 7, 2004 A. Ceccucci/ CERN 92
Reconstruction of K+ and K- beam spotsBeam spot size from K ∼ 7 cm2 Total Rate from π K ∼ 20 MHz
NA48/2
KABES IN NA48/2
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October 7, 2004 A. Ceccucci/ CERN 93
Time resolution
0.6 ns
Position and time resolutions
Tagged K track
Space resolution from drift time measurement:
70 μm
Time resolution: 0.6 nsUsing TOT to correct time
slewing
Tagging with reconstructed K± ± + -
(T0)KABES- (T0)DCH Spectrometer (ns)
XStation 1 or 2 - XStation 3 (cm)
NA48/2KABES IN NA48/2
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October 7, 2004 A. Ceccucci/ CERN 94
Kaon Rare Decays and the SMC
P-Vi
olat
ion
(holy grail)
CP-Conservation
Kaons provide quantitative tests of SM independentfrom B mesons
NA48/3
|Vtd|NA48/4
NA48/5
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October 7, 2004 A. Ceccucci/ CERN 95
Photon Vetoes (KAMI)
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October 7, 2004 A. Ceccucci/ CERN 96
Trigger• INPUT: 10 MHz DC; The single rate particle is dominated by muons
from Kaon decays!! 2/3 of decays have 1 moun in filan state• Important to reduce rate using simple cuts to avoid correlations• MAMUD and ANTI used as a veto should reduce the rate to 2.5 MHz• LKR bidimensional pipelined trigger to count photons can be
envisaged now (follow LHC experience)• LKR will reduce rate to 1 MHz• Further suppression based on multiplicity in DCH, SAC, CHV • At this stage the rate will be sufficiently reduced to allow a processor-
based system to analyse the WC tracking information applying mild cuts on the missing mass ( 100 KZH?)
• High Level Trigger handled in PCFARM (cf. LHCB 1MHz level 1…)• ½ band-width reserved for down-scaled triggers• Others triggers to collect less rare but still very interesting kaon
decays
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October 7, 2004 A. Ceccucci/ CERN 97
SPIBES• Si Sensor
– Wafers of thickness < 150 micron can be obtained but bump-bonding yield needs to be investigated
– Experience gained by LHC experiments very valuable– To achieve 100 ps time resolution 90% of the charge from the
sensor has to be collected in ~1ns • Pixel chip (Mixed-signal ASIC)
– Very fast preamp and shaper– Very low time walk discriminator– High Resolution TDC
• Front-end hybrid– Additional functionality is needed for clock, trigger distribution,
data multiplexing and transmission, and controls– This requires one or more ASICs in the immediate vicinity of the
pixel chip– For this design, to minimise thickness it is desirable to have
power, data buses and the front-end hybrid functionality at the periphery of the detector plane
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October 7, 2004 A. Ceccucci/ CERN 98
SPIBES• Silicon micro-pixel good candidate to achieve
required time resolution– Capacitance of single pixel ~ 100 fF– Rise time requirement < 2 ns – Must be demonstrated in R&D phase
• The complexity of the analog/digital design with on-chip TDC capability will most likely require the use of 0.13 micron CMOS technology
• Hybrid Pixel Technology– Pixel chip bump-bonded on Si sensor– State-of-the-art: ALICE SPD 150 micron chip on 200 micron
sensor– Further reduction of material needs investigation
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October 7, 2004 A. Ceccucci/ CERN 99
0++, 2++
Direct CPV
Indirect CPV
CPC
K0L→0ee and K0
L→0
Study Direct CP-Violation
•Indirect CP-Violating Contribution has been measured (NA48/1, see next slide)•Constructive Interference (theory)•CP-Conserving Contributions are negligible
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October 7, 2004 A. Ceccucci/ CERN 100
K0S →0 ee and K0
S →0
KS →0 eeKS →0
BR(KS→0ee) 10-9 = 5.8 +2.8
-2.3(stat) ± 0.8(syst)
|as|=1.06+0.26-0.21 (stat) ± 0.07 (syst)
PLB 576 (2003)
7 events, expected back. 0.15
BR(KS→0) 10-9 = 2.9 +1.4
-1.2(stat) ± 0.2(syst)
|as|=1.55+0.38-0.32 (stat) ± 0.05 (syst)
La Thuile, Moriond 2004
6 events, expected back. 0.22
NA48/1 NA48/1
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October 7, 2004 A. Ceccucci/ CERN 101
Isidori, Unterdorfer,Smith:
Fleisher et al:
Ratios of B → modes could be explained by enhanced electroweak penguins
and enhance the BR’s:
* A. J. Buras, R. Fleischer, S. Recksiegel, F. Schwab, hep-ph/0402112
1.6 111.6
0.7 110.7
9.0 10
4.3 10
NPe e
NP
B
B
0 12L(K ) 10Br
0 12L( ) 10Br e e
K0L→0ee (): Sensitivity to New Physics
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October 7, 2004 A. Ceccucci/ CERN 102
Tentative Indication of costElement Cost (MCHF) CommentsBEAM LINE 0.5 Modified K12 lineCEDAR 0.2 Photon DetectorsGIGATRACKER 1.4 Assuming 0.13 m VACUUM 0.7 Upgrade of vacuum systemANTI 4.2 Based on CKM estimate + elec.WC 3.0 Two more chambers + R/OMNP33/2 2.5 Including prolongation of He tankCHOD 1.0 2000 PMs, 500 CHF/channelLKR 2.0 New supervion system and R/O
A state-of the art calorimeter is 15 MCHFMAMUD 2.0 Cost of iron: ~500 KCHFSAC & CHV 0.5TRIGGER & DAQ
TOTAL 19.0
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October 7, 2004 A. Ceccucci/ CERN 103
K0L → 0
•Purely theoretical error ~2%: SM 3 10-11
•Purely CP-Violating (Littenberg, 1989) •Totally dominated from t-quark•Computed to NLO in QCD ( Buchalla, Buras, 1999)•No long distance contribution SM~3 × 10-11
• Experimentally: 2/3 invisible final state !!• Best limit from KTeV using →ee decay
BR(K0 → 0) < 5.9 × 10-7 90% CL
Still far from the model independent limit: BR(K0 → 0) < 4.4 × BR(K+ → +) ~ 1.4 × 10-9 Grossman & Nir, PL B407 (1997)
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October 7, 2004 A. Ceccucci/ CERN Mara Martini 104
Estimation of the Radiation Effects for Future NA48
VERY PRELIMINARY! Fluence:
Assuming 5000 spills/day, 50MHz particles/cm2/spill and a spill length of 4.8s:
1.2E12 particles/cm2 per dayAssuming pion beam:
eq= …hardness factor (9GeV pions:3.6, flat dist.)eq=4.32E12 (1 MeV neutrons)/cm2 per day
Assuming 100 days of running:eq= 4.32E14 (1 MeV neutrons)/cm2 per
run
>> Leakage current, depletion voltage, signal, operating conditions,….
Dose: 4.32E14/(6.24E9/(1.66 MeV g-1 cm2))=114kGy= 12 Mrad
Need an accurate investigationNeed an accurate investigation !
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October 7, 2004 A. Ceccucci/ CERN 105
Comparison with TDC
TDCFADC
• Leading time distribution
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October 7, 2004 A. Ceccucci/ CERN 106
FADC data (3)
• Pulse height distribution
– Threshold ~37 ADC counts
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October 7, 2004 A. Ceccucci/ CERN 107
Data without Zero-supp (baseline)
• Baseline:– Mean: 20.2– R.m.s.: 2.4
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October 7, 2004 A. Ceccucci/ CERN 108
Unexpected very big pulses (1)
• ADC count 255 = 400 mV
• width of this pulse: ~450 ns
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October 7, 2004 A. Ceccucci/ CERN 109
Unexpected very big pulses (2)
occupies the wholeFADC R/O time window!
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October 7, 2004 A. Ceccucci/ CERN 110
Unexpected very big pulses (3)
• Fraction of “big” pulses (>200 ADC counts) over “normal” pulses (<200 ADC counts) as a funcion of beam intensity