Transcript Diapositiva 1

Physics Motivation
• Kaon Physics
• Vus to per mil level (Ks →en)
• Ks → 3
• Lepton universality
• Test of CPT
• Charge asymmetry of semileptonic decays
• Quantum Interferometry
including searches via gg coupling
• eta/eta’ physics
• Dalitz and double-dalitz decays
• eta, eta’ → 3
FF
ChPT
• C, CP forbidden decays
• Scalar physics
including searches via gg coupling
• Multihadron cross section measurements
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DETECTOR UPGRADES
B field
Vertex chamber
Calorimeter granularity
DC z coordinate read out
NECESSARY UPDATES
Trigger
FEE-DAQ
Software
KS  
But, on the other hand
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We are evaluating the
effect of a lower B field
on
the
detector&reconstruction
performance, namely:
➢ Increase the acceptance
for low momentum (<100
Mev/c) tracks coming
from IP.
➢ Reduction of spiralizing
tracks  less broken
tracks, less tails in
momentum resolution
Worsening the resolution on the reconstructed Pt expecially for
tracks whose reconstruction accuracy is not dominated by M.S.
(momentum >150 MeV/c)
Magnetic field value
dramatically affects signal
acceptance. Can improve
up to a factor ~ 2
 (KLCrash + Ks DC selection)
0.2
T. Spadaro
0.15
0.1
Proper balancing with
consequent loss in
momentum resolution yet
to be studied
Present analysis, MC with
0.05 detailedfield map
400 pb MC with LSF=0.5,
with uniform axial B field
0
3
5 B (kG)
4
5 KGauss
4 Kgauss
3 KGauss
The loss of resolution due to
B lowering must also be
folded
with
change
in
vertexing capability.
Muon momentum in K± CM (MeV)
p (MeV)
For example in the 2 body
decay of K± (Ke2/K2) the
reduction of > 40% in B field
translates in a loss < 15% in
the resolution of the muon
momentum in the K charged
center of mass
Resolution on the  peak
B field (KGauss)
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POSSIBLE UPGRADES
B field
Vertex chamber
Calorimeter granularity
DC z coordinate read out
NECESSARY UPDATES
• Trigger
• FEE-DAQ
• Software
In KLOE as it is now the first hit of DC is at a radius of
28 cm from IP.
Almost any item of the KLOE2 physics programs would
benefit from a vertex detector. In particular,
✔ gain in acceptance for low momentum tracks,
✔ better resolution for the KL,KS decay vertex near IP
✔ greater efficency for the K± reconstruction
are solid reasons for this new hardware . No technical
solution have been yet spotted.
Here we gives some general figures about: acceptance,
thickness , resolution, occupancy
f KSKL 
I(, ;Dt) (a.u.)
Black hist. : (Dt)~tS =>6mm
Red hist: (Dt)~/4 tS =>1.5mm
Blue curve: ideal
Dt/tS
The detector radii are dictated
by physics (inner) and clearance
(outer)
10 cm
10 cm
25 cm
Vertex detector: size
To preserve kaons interference the vertex should have the inner
layer at radius not much lower than 12 cm (20 tKS)
To attempt independent reconstruct of the track helix at least 3(4)
planes must be envisaged, with a spacing of the order of 1-2 cm.
To maximize the acceptance a length twice the radius is needed (4070 cm)
70 cm
15000cm2
12 cm
30 deg
e-
20 cm
e+
pions,muons
p/p
p/p
Comparison between MS induced by 2 reference value of silicon
thickness (1mm and 1.5 mm) wrt a KLOE-like:≈ 700 m of carbon fiber.
A thickness larger than 1mm of silicon equivalent (≈ 1% of X0) can be a
limiting factor for the momentum mesurement of low momentum
particle coming from IP .
Problem can also be given by the conversion of photons from machine
Silicon 1.5mm
silicon 1mm
1%
KLOE
P (MeV/c)
electrons
Silicon
muons1.5mm
muons
silicon 1mm
1%
KLOE
P (MeV/c)
For interference studies this detector should
achieve on the KS decay point an accuracy better of
mm. (tS≈0.6 cm)
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If an independent tracking should be attempted the
hit resolution should be such to keep dpt/pt at
the order of the MS contribution ≈ few %
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A hit resolution of 10000 m for a typical track length of 10 cm
with 3(4) points per track could be sufficient.
Resolution seems not to be critical, but must be obtained on a large
active surface (15000 cm2)
No choice has been made for this crucial item. Accurate
simulation and integration of the reconstruction software
in the KLOE environment are needed to disantangle the
different features of the possible detectors. In general
three different detectors have been considered:
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Silicon detector: possibly 3D space measurement, well
estabilished technology. DE/DX measurement could be a bonus
Light drift chamber, with stereo geometry wires and charge
division for z coordinate. Estrapolation toward IP of the KLOE DC
Cilindrical GEM : new technology, 3D coordinate, GEM know-how
present at LNF. Interest by DDG-LNF group (G.Bencivenni)
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POSSIBLE UPGRADES
B field
Vertex chamber
Calorimeter granularity
DC z coordinate read out
NECESSARY UPDATES
• Trigger
• FEE-DAQ
• Software
ECAL granularity
The calorimeter cell has a size of
4.4x4.4 cm2, to be compared with a
Moliere radius of the order of 1.5 cm.
A finer granularity could help in:
avoid cluster splitting
 avoid clusters merging
 allow better cluster shape analysis
for PID
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Any analysis based on cluster counting
is affected; as esample of cluster
splitting effect we refer to KS  30
analysis (bck from KS20 + double
splitting)
80
Data
MC KS  30
6 gs events !!
60
40
20
00
10
20

30
40
Cluster merging effect: the  gg decay
After cutting on the kinematic fit 2 in
the fgggg
hypothesis, a huge background
survives, entirely due to 
decays with double merged clusters.
Due to the merging of two couple of
photons the topology of 
becomes equal to the gg
The invariant mass of the four
photons peaks as the signal. The
two plots are scaled according the
real branching ratios:
By integrating only the mass peak region we get
To study the cluster merging/splittting vs the read-out granularity we used
the FLUKA package to simulated a KLOE ECAL module:
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Geometry and materials are reproduced in details.
Digitization has been implemented on a fiber by fiber basis.
Granularity can be easily changed
Clustering algorithm implementation under way
electron showers– 200 MeV
spaced by 1 cell (4.4 cm)
muon showers– 200 MeV
spaced by 1 cell (4.4 cm)
1000 events
KLOE
cell size
depth (cm)
depth (cm)
ECAL readout
• A complete change in the ECAL granularity to 2x2 means x4 in
FEE channels. Can be studied by FLUKA MC the effectiveness of
targeted changes (i.e. Only last and/or first plane, etc..)
• The KLOE photomultipliers has good q.e. (25%) and very good
timing. Any change in photodetector must save the excellent
timing capabilities of KLOE.
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A viable solution could be to use multi anode pmt. For example
R7600-00M16 or M64 or M4 by Hamamatsu with very good
risetime and similar q.e. . Under test in ROMA3
• The amount of work coming from mechanics and lightguides
preparation and setup must not be underestimate
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POSSIBLE UPGRADES
B field
Vertex chamber
Calorimeter granularity
DC z coordinate read out
NECESSARY UPDATES
• Trigger
• FEE-DAQ
• Software
The pattern recognizes the track helix in the separated stereo
views where the helix projections are ellipses. Then the two
separate 2d tracks are merged into a single 3d object. The
possibilities to have the z coordinate would help to avoid track
splittings, fake vertexes, resolution tails.
example from K+K
The KLOE wire are not well suited
for charge division (RW ≈400 W)
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Test are foreseen to verify the
possibility of achieving the
modest resolution (1-2 % x LW)
needed for the pattern
DE/DX measurement would be
greatly improved
11000 channels x 2 of ADCs....
Split
track
Split track, no
VTX
reconstructed
NECESSARY UPDATES
• Trigger
• FEE-DAQ
• Software
Project Status
• Work in progress on different issues of the detector upgrade,
including the cost evaluation
• LoI to be circulated by end of March
– The first meeting held yesterday : 40 participants from at least 6
Institutions - including Karlsruhe Krakow Mainz Uppsala