Physics Motivation• Kaon Physics

• Vus to per mil level (Ks →e

• Ks → 3

• Lepton universality

• Test of CPT

• Charge asymmetry of semileptonic decays

• Quantum Interferometry

• eta/eta’ physics including searches via coupling

• Dalitz and double-dalitz decays FF

• eta, eta’ → 3 ChPT

• C, CP forbidden decays

• Scalar physics including searches via coupling

• Multihadron cross section measurements

DETECTOR UPGRADESDETECTOR UPGRADES• BB field• Vertex chamber • Calorimeter granularity• DC z coordinate read out

NECESSARY UPDATESNECESSARY UPDATES• Trigger• FEE-DAQ• Software

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

But, on the other hand

● Worsening the resolution on the reconstructed Pt expecially

for tracks whose reconstruction accuracy is not dominated by M.S. (momentum >150 MeV/c)

KS

Magnetic field value dramatically affects signal acceptance. Can improve up to a factor ~ 2

Proper balancing with consequent loss in momentum resolution yet to be studied

B (kG)

(KLCrash + Ks DC selection)

Present analysis, MC with detailed field map400 pb MC with LSF=0.5, with uniform axial B field

0.1

0.2

3 540

0.15

0.05

T. Spadaro

The loss of resolution due to B lowering must also be folded with change in vertexing capability.

For example in the 2 body decay of K± (Ke2/K2)

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

5 KGauss4 Kgauss3 KGauss

Muon momentum in K± CM (MeV)

B field (KGauss)

p (M

eV) Resolution on the peak

POSSIBLE UPGRADESPOSSIBLE UPGRADES• BB field• Vertex chamber • Calorimeter granularity• DC z coordinate read out

NECESSARY UPDATESNECESSARY 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

Black hist. : tS =>6mm

Red hist: tS =>1.5mm

Blue curve: ideal

KSKL

t/S

I(, ;t) (a.u.)

10 cm

10 cm

25 cm

The detector radii are dictated by physics (inner) and clearance (outer)

To preserve kaons interference the vertex should have the inner layer at radius not much lower than 12 cm (20 KS)

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

(40-70 cm)

12 cm

20 cm

e+e-

70 cm

Vertex detector: size

30 deg

15000cm2

Comparison between MS induced by 2 reference value of silicon thickness (1mm and 1.5 mm) wrt a KLOE-like:≈ 700m 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

P (MeV/c)

electrons

muonsmuons

pions,muons

silicon 1mm

Silicon 1.5mmSilicon 1.5mm

silicon 1mm

KLOEKLOE

P (MeV/c)

p/p

p/p

1%1%

➢ For interference studies this detector should achieve on the K

S decay point an accuracy better of

mm. (S≈0.6 cm)

➢ If an independent tracking should be attempted the hit resolution should be such to keep dp

t/pt at

the order of the MS contribution ≈ few %

➢ A hit resolution of 10000 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:

● 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)

POSSIBLE UPGRADESPOSSIBLE UPGRADES• BB field• Vertex chamber • Calorimeter granularity• DC z coordinate read out

NECESSARY UPDATESNECESSARY 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

Any analysis based on cluster counting is affected; as esample of cluster splitting effect we refer to KS 30 analysis (bck from KS20 + double splitting)

DataMC KS 30

00

20

40

80

60

4010 20 30

6 s events !!

Cluster merging effect: the decay

After cutting on the kinematic fit 2 in the 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 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:

● 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

depth (cm) depth (cm)

electron showers– 200 MeVspaced by 1 cell (4.4 cm)

muon showers– 200 MeVspaced by 1 cell (4.4 cm)

KLOEcell size

1000 events

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.

• 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

POSSIBLE UPGRADESPOSSIBLE UPGRADES• BB field• Vertex chamber • Calorimeter granularity• DC z coordinate read out

NECESSARY UPDATESNECESSARY 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.

Split track

Split track, no VTX reconstructed

The KLOE wire are not well suited for charge division (RW ≈400 ) .

● 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....

example from K+K

NECESSARY UPDATESNECESSARY 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