status report of dirac

Status Report of DIRACStatus Report of DIRAC

SPS and PS experiments CommitteeSPS and PS experiments CommitteeL. NemenovL. Nemenov 22 April 200822 April 2008

DIRAC Addendum

LIFETIME MEASUREMENT OF AND ATOMS TO TEST LOW-ENERGY QCD

K

DIRAC collaborationDIRAC collaborationCERN Geneva, Switzerland

Zurich University Zurich, Switzerland

Kyoto Sangyou University Kyoto, Japan

Bern University Bern, Switzerland

KEK Tsukuba, Japan

Basel University Basel, Switzerland

Santiago de Compostela University Santiago de Compostela, Spain

University of Messina Messina, Italy

IHEP Protvino, RussiaTrieste University and INFN-Trieste

Trieste, Italy

SINP of Moscow State University Moscow, Russia INFN-Laboratori Nazionali di Frascati

Frascati, Italy

JINR Dubna, Russia

Nuclear Physics Institute ASCR Rez, Czech Republic

IFIN-HH Bucharest, Romania

Institute of Physics ASCR Prague, Czech Republic

Tokyo Metropolitan University Tokyo, Japan

Czech Technical University Prague, Czech Republic

75 Physicists from 19 Institutes


OutlineOutline

I. RUN 2007. 1. Main tasks 2. Upgrade setup. 3. Characteristics of the new detectors. 4. Data taking. 5. Status of the data process. II. RUN 2008. 1. Main tasks. 2. Status of the new electronics and DAQ. 3. RUN schedule. III. A2π lifetime measurement and expected physical results after RUN 2008 and RUN 2009.


Plan for the run 2007Plan for the run 2007

• Tuning of all detectors downstream the magnet

• Start of the data taking towards the first observation of AπK and AKπ

• Tuning of the Scintillating Fiber Detector and the Ionization hodoscope with the new electronics in parallel with data taking.

•Tuning of the Micro Drift Chambers in parallel with data taking.


Method of Method of AAπK πK and and AAKπ Kπ observationobservationand lifetime measurementand lifetime measurement

Main features of the DIRAC set-up

Thin targets: ~ 7 ×10–3 X0, Nuclear efficiency: 3 ×10−4

Magnetic spectrometerProton beam ~ 1011 proton/spill

Resolution on Q: Qx≈ Qy≈ QL≈ 0.5 MeV/c

“atomic pairs”

(AπK) is too small to be measured directly

e. m. interaction of AπK in the target

AπK → π+K −

AKπ → K+π −

Q < 3MeV/c, ,Θlab< 3 mrad

• Coulomb from short-lived sources• non-Coulomb from long-lived sources

KK

mp p

m

“free pairs”

Target Ni 98 m

AπK

p

24 GeV/c

p

24 GeV/c

π+

K−


K−

π+

Trajectories of Trajectories of ππ−− and and KK++ from the from the AAπKπK break-up break-up

The numbers to the right of the tracks lines are the π and K + momenta in GeV/c

The AKπ, π − and K +

momenta are shownin the following table:

Patom

(GeV/c)

Pπ

(GeV/c)

PK

(GeV/c)

5.13 1.13 4.0

5.77 1.27 4.5

6.41 1.41 5.0

10.26 2.26 8.0


Upgraded DIRAC experimental setupUpgraded DIRAC experimental setup


Upgraded DIRAC experimental setup descriptionUpgraded DIRAC experimental setup description


All Cherenkov detectorsAll Cherenkov detectors


Cherenkov detector CCherenkov detector C44FF1010 I IResponsibility: JINR (Dubna, Russia) with participation of INFN (Frascati National Lab, Italy); IFIN-HH (Bucharest, Romania); Zurich University (Zurich, Switzerland); Adviser: O. Ullaland (CERN)


Cherenkov detector CCherenkov detector C44FF1010 II II

2p.e 0 02 2

11 sin CN LN LN

n

4 10(C F ) 1.00135n

p.e.( 1) 30p.e.N

Cherenkov detector quality factor N0= 125 cm-1

Efficiency to detect pions with momenta >4Gev is >99.5%


Aerogel Cherenkov detector IAerogel Cherenkov detector IResponsibility: Zurich University (Zurich, Switzerland)


Aerogel Cherenkov detector IIAerogel Cherenkov detector II

The n=1.008 counter

Status:Aerogel detectors were installed on the setup

Responsibility: Zurich University (Zurich, Switzerland)


Proton rejection efficiency for a cut in the ADC 20 channels above pedestal:• 94.2 % for the heavy aerogel @p= 4.5-5 GeV/c • 89.3 % for the light aerogel @p = 6-8 GeV/c

Kaon detection efficiency for the same cut:• 95.6 % for the heavy aerogel @p= 4.5-5 GeV/c • 92.4 % for the light aerogel @p= 6-8 GeV/c

n=1.015 module

Npe =6.9 Npe =3.9

n=1.008 module

Pure proton signal from Λ decay and TOF separation

Negative kaon spectrum for p=4.5 -5 GeV/c

Negative kaon spectrum for p = 6-8 GeV/c

Aerogel: Aerogel: Kaon and proton signal IIIKaon and proton signal III


2 4 6 8 100

Preshower detector IPreshower detector IResponsibility: IFIN-HH (Bucharest, Romania)


Preshower detector IIPreshower detector II


Scintillation Fiber Detector IScintillation Fiber Detector ISensitive area = 98.5 x 107 mm2


Scintillation Fiber Detector IIScintillation Fiber Detector II

Characteristics:

Size of the plane 100×100

mm2

Thickness of the material for one plane 3 mm (1%

X0)

Mean light output: ≈ 11

p.e.

Mean Detector Efficiency: ≈ 98

%

Time Resolution without coordinate and amplitude corrections ≈ 0.46

ns

Space resolution σ ≈ 60

m

New electronics (ADC-TDC for each channel) 960 channelsSPS and PS experiments CommitteeSPS and PS experiments Committee

L. NemenovL. Nemenov 22 April 200822 April 2008

Number of channels tested with F1• SFD-X : 464 channels (out of 480) • IH : all 64 channels

Number of channels tested with F1• SFD-X : 464 channels (out of 480) • IH : all 64 channels

Optimum threshold • SFD-X : ~15–20 mV• IH : ~20 mV

Optimum threshold • SFD-X : ~15–20 mV• IH : ~20 mV

TDC channel ADC channel ADC channel

Eve

nts

Eve

nts

Eve

nts

TDC spectrum SFD

Trigger peak

Background

ADC spectrum IH

Thr = 20 mV

Pedestal tail

ADC spectrum SFD

Pedestal + Single p.e. (light crosstalk)

Thr = 10 mV

Good events

Good events

~2.4 ns(FWHM)

SFD and IH with new TDC/ADC beam test 2007SFD and IH with new TDC/ADC beam test 2007


Main features:

High spatial accuracyσ < 30 µm (2004 result);

Distinguish two close tracks with distance < 200 µm;

Efficiency > 98% at I = 2×1011 protons/spill;

total detector thickness <5×10-3 X0;

time resolution < 1 ns;

readout time < 3 s.

Responsibility: JINR (Dubna, Russia), Basel University (Basel, Switzerland)

Micro Drift Chambers IMicro Drift Chambers I


Examples of event Status

During 2007 run Micro Drift Chambers with the new electrodes and all electronics were finally implemented into the DIRAC setup and DAQ system. Data with different MDC working condition were collected.

Online data 2007

Target: Pt (28µm)Intensity: 2x1011

Micro Drift Chambers IIMicro Drift Chambers II


Drift time: τ ~ 23ns

Beam profile, reconstructed by MDC

Micro Drift Chambers IIIMicro Drift Chambers III


• Improvement of the proton beam time structure and the beam intensity distribution at spills. R.Steerenberg, A.Grudiev, L.Gatignon et al.

• Beam intensity about 1.91011 proton/spill 1st level triggers numbers 3200(π+π−)+2100(K+π−)

+1000(π+K−)=6300 1/spill

• Number of recorded events 2000 1/spill is near to the hardware limit of DAQ

• Full number of π+π− and πK events recorded during 3 months of data taking is 1.4109

Run 2007Run 2007


Estimation of AK and AK atom fluxes

2 14

K K

N A

N A A

Assuming an additional factor of inefficiency for kaonic atoms of 2 and using expected value of the lifetime 3.7 fs we estimate the number of collected kaonic atoms: nAπK +nAKπ = 700 ± 200. This value coincides with the estimations made in Addendum and reported at SPSC last year.

First estimation of A2π observed in 2007 with Pt target: 10000±3000 (with suppression factor 2 in respect to πK atom trigger)

From theory and FRITIOF6 simulation production of atoms relates as:


Before autumn 2008 we will prepare a paper titled:“Search for πK atoms” or “Observation of πK atoms”

RUN 2008 Main tasks.RUN 2008 Main tasks.

• To tune DIRAC setup with the new front-end electronics, trigger logic, readout system and DAQ

• To perform data taking for the lifetime measurement of A2π , AKπ and AπK


Responsibility: JINR (Dubna, Russia) with participation of IFIN-HH (Bucharest, Romania);

Zurich University (Zurich, Switzerland)

Front-end electronics and Readout SystemFront-end electronics and Readout System

1 Logical output signals for trigger (flat cables)

Exp

eri

me

nta

l A

rea

Ba

rrac

k

USB

Host computer

USB hubs

Central storage (IT division)

ČVH HH …

ADC-TDC(D412)

1

SFD

Transmitter(1st level)

2

2 ADC&TDC signals for readout (maximal distance ~10 m)

ADC-TDC(D412)

ADC-TDC(D412)

ADC-TDC(D412)

ADC-TDC(D412)

11 1 12 2 2 2





Transmitter(2nd level)

Transmitter(2nd level)


Status of the new electronicsStatus of the new electronics

• All electronics is ready, tuned and will be installed before the rung beginning

• The setup tuning, in according to our plan, will be done during 6 weeks

Data taking will continue 4 monthsData taking will continue 4 months


Pion scattering lengthsPion scattering lengthsLow-energy QCD predictions for ππ scattering lengths (s-wave):

1) 1977 Geneva-Saclay: (PR D15, 574)

a0 0.220 2.3%

a2 0.0444 2.3%

a0 a2 0.265 1.5%

ExperimentsExperimentsK → π+π e+ve(Ke4):

a0 0.28 18%

2) 2001 E865 / BNL: (PRL 87, 221801)

a0 0.20316%

a2 0.055 42%

3) 2008 NA48 / 2: (EPJ C54, 411)

a2 0.047123%(stat) 8%(sys)

a0 0.2337%(stat) 3%(sys) ... 7.5% *)

2006 NA48 / 2:(PL B633, 173)

K → π0π0π+:

a0 a2 0.2683.7%(stat) 1.5%(sys) 4.8%(ext) ... 6.2%

*) using Roy equations

*)


*)

Experimental results 2001-2003Experimental results 2001-2003


>2008 DIRAC: ...after data collection in 2008 & 2009

3) >2008 DIRAC: ...after data collection in 2008 & 2009

Experimental resultsExperimental resultsLow-energy QCD predictions for scattering lengths (s-wave):

1) 2005 DIRAC: (PL B619, 50) ...based on 2001 data (6530 observed atoms)

a0 a2 0.265 1.5%

ExperimentsExperimentsA2π lifetime:

a0 a2 ...2%(stat) 1%(sys) 1%(th) ... 2.4%

a0 a2 0.264 7.5%(stat) 83%(sys) ... 11

8%

2) 2008 DIRAC: preliminary ...from major part 2001-03 data (13390 observed atoms)

a0 a2 0.268 4.5%(stat) 2.21.9%(sys) ... 5.0

4.9%

AπK lifetime:

1 3 ... 10%( )a a stat

a1 a3 0.269 6% (RS)

a1 a3 0.24 (1 loop)ππ: πK:


Run 2009 will increase the statistics of A2π , AπK and AKπ on factor 2.5

Run 2009Run 2009


The measurement of the s-wave πK scattering

lengths would test our understanding of the chiral

SU(3)L SU(3)R symmetry breaking of QCD (u, d

and s quarks), while the measurement of ππ

scattering lengths checks only the SU(2)L SU(2)R

symmetry breaking (u, d quarks).

What new will be known if K scattering length will be measured?

KK scattering scattering

This is the main difference between ππ and πK scattering!


status report of dirac

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