M. Oberholzer, K.Brauchli, K.D.Kunze University Hospital Basel, Switzerland
Presented by L. Tauscher Basel University, Switzerland
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L. Nemenov, EXA05 Using - and -K atoms for the experimental check of low-energy QCD L. Nemenov (CERN, Switzerland) Presented by L. Tauscher Basel University, Switzerland
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Using - and -K atoms for the experimental check of low-energy QCD L. Nemenov (CERN, Switzerland). Presented by L. Tauscher Basel University, Switzerland. Why atoms ?. Particles scatter off each other in well defined atomic quantum states - PowerPoint PPT Presentation
Transcript of Presented by L. Tauscher Basel University, Switzerland
L. Nemenov, EXA05
Using - and -K atoms for the experimental check of low-energy
QCD L. Nemenov (CERN, Switzerland)
Presented by
L. Tauscher
Basel University, Switzerland
L. Nemenov, EXA05
Why atoms ?•Particles scatter off each other in well defined atomic quantum states•Very low Q’s atomic level scheme sensitive to scattering length
Strong interaction leads to complex energy eigenvaluesEnl - i nl/2 = Enl
QED + nl - i nl/2Example:
1S 2a0 + a2 1S |a0 - a2|2
“Model-independent” determination of scattering lengths
L. Nemenov, EXA05
Experimental status on K++-e+ve (Ke4) phase difference
(s)-(s) for 4m
<s<mK2
a0 = 0.26 ± 0.05[m] Roy eq. Rosselet et al. CERN 1977
a0 = 0.203 ± 0.033[m] Roy eq. Pislak et al. BNL / E865
a2 = -0.055 ± 0.023[m] 2001/2003
a0 = 0.216 ± 0.013stat ± 0.004syst ± 0.002th [m] Roy eq
a2 = from ChPT
DIRAC (A) after analysis of ALL collected data so far |a0-a2| ± 5%stat (± 3%syst ± 2%th)estimated
± 0.013stat (± 0.008syst ± 0.005th)estimated
L. Nemenov, EXA05
Theory
a0 = 0.220 ± 0.005 [m] (2.3%)
a2 = -0.0444 ± 0.0010[m] (2.3%)
a0- a2 = 0.265 ± 0.004 [m] (1.5%)
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Theory
L. Nemenov, EXA05
Experimental status on In the 60’s and 70’s set of experiments were performed to measure πK scattering amplitudes. Most of them were done studying the scattering of kaons on protons or neutrons, and later also on deuterons. The kaon beams used in these experiments had energies ranging from 2 to 13 GeV. The main idea of those experiments was to determine the contribution of the One Pion Exchange (OPE) mechanism. This allows to obtain the πK scattering amplitude. Analysis of experiments gave the phases of πK-scattering in the region of 0.7 ≤ m(πK) ≤ 2.5 GeV. The most reliable data on the phases belong to the region 1 ≤ m(πK) ≤ 2.5 GeV.
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Theoretical accuracy on atomic quantities
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Theoretical accuracy on atomic quantities
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Principle of lifetime measurement
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Pbr to lifetime conversion
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DIRAC II (Addendum)
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DIRAC II Set-up
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DIRAC II Set-up
Decrease the systematic errors.1. Single–multilayer targets 2. Identification of e±, ±, K ± and p
Increasing of statistics and efficiency of the setup • Shielding K ≈ 1.9
Formation of time structure of the spill with the trigger of setup
Microdrift chambers
New electronics for SFD
Increase in the aperture on VH hodoscope and PSH Total K ≈ 4
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Metastables
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Metastables
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Metastables
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Metastables
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Metastables
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Metastables
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Metastables
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Metastables
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Metastables
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Prospects beyond DIRAC II
Measure at machines with •higher proton current•Higher duty factor•Higher energy
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Yields of atoms as a function of the proton beam momentum
Yields of pion pairs and atoms for 24 GeV protons per pNi-interaction at Θlab=5.7° (DIRAC accept.)
P, GeV/c +- A2 A2/+- AK+AK (AK+AK)/+-
24 2.1·10-2 0.95·10-9 4.4·10-8 0.83·10-10 0.39·10-8
Relative yields of pion pairs and atoms as a function of the proton beam momentum
P, GeV/c +- A2 A2/+- AK+AK (AK+AK)/+- Duty factor
PS CERN 24 1 1 1 1 1 1(0.06)
GSI (SIS100)
30 1.2 1.4 1.14 1.5 1.26 8.4
J-PARC 50 1.6 2.2 1.43 2.8 1.74 3.3
GSI (SIS200)
60 1.8 2.6 1.52 3.5 1.91 8.4
GSI (SIS300)
90 2.0 3.4 1.72 4.6 2.30 8.4
SPS CERN 450 3.1 12 3.7 13.5 4.3 4.0
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Estimation of error sources in |a0-a2|/ |a0-a2|
based on data taken with the upgraded DIRAC setup
during 12 months (20h/day)
Single-layer target
nA stat τ=f(a0-a2) Pbr=f()*) Non-pointli
ke produc
tion
PS CERN
24 GeV/c
85000 2% 0.6% 1.2% 1%
J-PARC
50 GeV/c
4.1*105 0.9% 0.6% 1.2%
GSI
90 GeV/c
1.2*106 0.6% 0.6% 1.2%
SPS CERN
450 GeV/c
1.26*106 0.5% 0.6% 1.2%
*) Precision of Pbr=f() can be increased to better then 0.6%private communication by D.Trautmann
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Estimation of error sources in Δ|a1/2-a3/2|/ |a1/2-a3/2|
based on data taken with the upgraded DIRAC setup
during 12 months (20h/day)
Single-layer target
nA stat τ=f(a1/2-a3/2) Pbr=f()
*)
syst
PS CERN
24 GeV/c
7000 10% 1.1% 1.2%
J-PARC
50 GeV/c
1.7*104 7% 1.1% 1.2%
GSI
90 GeV/c
1.4*105 2.5% 1.1% 1.2%
SPS CERN
450 GeV/c
1.2*105 2.5% 1.1% 1.2%
*) Precision of Pbr=f() can be increased to better then 0.6%private communication by D.Trautmann
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Conclusions
