Post on 27-May-2020
Mem
berof
theHelmho
ltz-Associatio
n
Strangeness Production at COSY
September 07, 2015 Florian Hauenstein HYP2015, Sendai, Japan
Mem
berof
theHelmho
ltz-Associatio
n
Physics Program at COSYNon-perturbative QCD in the up, down and strange sector
Structure of hadronsnucleonshyperonsmesons
Dynamics and interactionsnucleon-nucleon (NN)nucleon-hyperon (NY )nucleon-mesonmeson-nucleus, in medium effects
Symmetries and symmetry breakingchiral symmetryisospin and charge symmetry in reactionsdiscrete symmetries in meson decays
September 07, 2015 Florian Hauenstein Slide 2
Mem
berof
theHelmho
ltz-Associatio
n
COSY FacilityCOoler SYnchroton
Circumference: 184mBeam momentum: 0.3GeV/c -3.7GeV/cStochastic and electron cooling(Un-)Polarized proton anddeuteron beams
September 07, 2015 Florian Hauenstein Slide 3
Mem
berof
theHelmho
ltz-Associatio
n
COSY-TOF: Physics Program
Meson production in pp collisionsStudy of pp → ppγExclusive hyperon production in pN → NKY with polarizedand unpolarized beams
production mechanism of associated strangenessNY interaction through final state interaction (FSI)NΛ− NΣ coupled channel effectnucleon excited states (N∗ resonances)polarization observables
Recent studies:~pp → pKΛ at pbeam = 2.7GeV/c with ≈ 78% polarization~pp → pKΛ at pbeam = 2.95GeV/c with ≈ 88% polarizationpn→ NKΛ at pbeam = 2.95GeV/c
September 07, 2015 Florian Hauenstein Slide 4
Mem
berof
theHelmho
ltz-Associatio
n
COSY-TOF DetectorTime Of Flight
STTRing
Quirl
Barrel
Start SQT
Calorimeter
p
p
K+
-
pBeam
3m
Features:
Full phase space coverage
Clear signature forpKΛ→ pK pπ(2 primary and2 secondary tracks)
Primary and delayedhyperon decay vertex(cτ(Λ) = 7.89 cm)
Latest Measurements of ~pp → pKΛ:
2.95GeV/c with (61.0± 1.7) % polarization → 42,000 events
2.95GeV/c with (87.5± 2.0) % polarization → ∼ 132,000 events
2.70GeV/c with (77.9± 1.2) % polarization → ∼ 220,000 eventsSeptember 07, 2015 Florian Hauenstein Slide 5
Mem
berof
theHelmho
ltz-Associatio
n
Physics of ~pp → pKΛ
Described by meson exchange models (no perturbative QCD)Which kind of meson exchangeRole of N∗ resonances
p
p
K
K
p
Λ p
p
π
K
Λ
p p
p
π
K
Λ
p
N*
[MeV/c^2]Λp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260
)2N
/A/(
2MeV
/c
500
1000
1500
2000
2500
3000
3500
]2 [MeV/cΛp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260
A
00.10.2
0
2.95GeV/c
nΣ+ pΣ0
M. Roeder, Eur. Phys. J. A49, 157 (2013)
pΛ− NΣ coupled channel (cusp)effect
pΛ final state interaction (FSI)
Connection to pΛ interaction→ Parameter: scattering length a
limk→0
σpΛ→pΛ = 4πa2
September 07, 2015 Florian Hauenstein Slide 6
Mem
berof
theHelmho
ltz-Associatio
n
Determination of pΛ Scattering LengthMethod from A. Gasparyan et al., Phys. Rev. C69, 034006 (2004)
Extraction of pΛ scattering length a from the shape of thefinal state interaction (FSI)No further theoretical assumption necessaryKnown theoretical precision (0.3 fm)Spin resolved measurement via suitable polarization observable
[MeV/c^2]Λp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260
)2N
/A/(
2MeV
/c
500
1000
1500
2000
2500
3000
3500
]2 [MeV/cΛp m2060 2080 2100 2120 2140 2160 2180 2200 2220 2240 2260
A
00.10.2
0
2.95GeV/c
nΣ+ pΣ0
COSY-TOF measurement at2.95GeV/c (42,000 events)M. Roeder et al., Eur. Phys. J. A49, 157 (2013)
Effective scattering lengthaeff = (−1.25± 0.08stat. ± 0.3theo.) fm
Large systematic error (1 fm) due tokinematical reflection of N∗ resonance
September 07, 2015 Florian Hauenstein Slide 7
Mem
berof
theHelmho
ltz-Associatio
n
Dalitz Plot Dependence on Beam MomentumNΣFSI
COSY-TOF Coll., Phys. Lett. B688, 142 (2010)
Contributions of N∗ change with beam momentaExpected smaller systematic effect on FSI for 2.7GeV/c?
⇒ Comparison of results from the recent data at 2.7GeV/c (∼132,000 events) and 2.95GeV/c (∼ 220,000 events)
September 07, 2015 Florian Hauenstein Slide 8
Mem
berof
theHelmho
ltz-Associatio
n
~pp → pKΛ Dalitz Plot
]4/c2 [GeV2Λp m
4.2 4.3 4.4 4.5 4.6 4.7
]4
/c2
[G
eV
2Λ
K
m
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
0
50
100
150
200
250
300
350
400
preliminary
2.7GeV/c
Hauenstein, PhD Thesis, 2014
2.7GeV/cMonte Carlo acceptance
2.95GeV/c
preliminaryJowzaee, PhD Thesis, 2014
Full phase space acceptance
Reconstruction efficiency relativelyflat
Strong pΛ final state interaction forboth data sets
More substructures for 2.95GeV/cSeptember 07, 2015 Florian Hauenstein Slide 9
Mem
berof
theHelmho
ltz-Associatio
n
Effective pΛ Scattering Length
/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06
)2 (MeV/cΛp m2060 2080 2100 2120 2140 2160
))2 (
nb
/(M
eV/c
Λp
/d
mσ
d
0
50
100
/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06
/ ndf 2χ 44.82 / 36 0C 0.0317± -0.1393 1C 7.663e+03± 1.211e+05 2C 3.470e+03± 4.158e+06
preliminary
2.7GeV/c
)2 (MeV/cΛpm2060 2080 2100 2120 2140 2160
(ar
b. u
nit
s)2 |
A~ |
0
2
4
6 / NDF = 1.252χ = -1.39e-01 + 3.06e-02 - 3.25e-020C
= 1.21e+05 + 7.99e+03 - 7.26e+031C
= 4.16e+06 + 3.32e+03 - 3.58e+032C
2.7GeV/c
preliminary
fit limit fit limitdσ
dmpΛ/PS
Parametrization: dσdmpΛ
= PS ·∣∣∣A(FSI )
∣∣∣2 = PS · exp[C0 + C1
m2pΛ−C2
]aeff = (−1.38+0.04
−0.05stat. ± 0.12syst. ± 0.3theo.) fm (preliminary)
Compatible with the result at 2.95GeV/c(aeff = (−1.25± 0.08stat. ± 0.3theo.) fm)
Systematic error mainly due to influence of N∗ resonances→ but weaker than for 2.95GeV/c (1 fm)
September 07, 2015 Florian Hauenstein Slide 10
Mem
berof
theHelmho
ltz-Associatio
n
Spin Triplet pΛ Scattering Lengthsee Appendix B in Gasparyan et al., Phys. Rev. C69, 034006 (2004)
pΛ in S-wave and kaon in P-wave ⇒ pΛ in spin tripletconfiguration due to parity and angular momentum conservation
Kaon analyzing power AKy sensitive to kaon P-wave contribution
AKy (X ,mpΛ) ≈ α(mpΛ)P1
1 (X ) + β(mpΛ)P12 (X )
Kaon P-wave contribution proportional to AKy (cos θ = 0) = −α
→ α gives relative contribution of spin triplet scattering→ Measurement of α dependence on mpΛ to determine spin tripletscattering length using the formula
|A(FSI )t(mpΛ)|2 = −α(mpΛ) ·∣∣∣A(FSI )eff(mpΛ)
∣∣∣2September 07, 2015 Florian Hauenstein Slide 11
Mem
berof
theHelmho
ltz-Associatio
n
Kaon Analyzing Power at 2.7GeV/cFit with associated Legendre polynomials and dependence on mpΛ
)2 (MeV/cΛpm2060 2080 2100 2120 2140 2160
Leg
end
re p
oly
no
mia
l co
effi
cien
ts
-0.2
-0.1
0
0.1
0.2 α
β
)CMSKθcos(
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
kao
n a
nal
yzin
g p
ow
er
-0.1
0
0.1
0.2
)2
1 P• β + 11 P• αfit (
)θ (cos11 P• α
)θ (cos2
1 P• β
/ NDF = 0.752χ
0.005± = -0.143 α 0.004± = 0.036 β
preliminary
preliminary
full data
Reasonable fit of analyzing power by AKy = αP1
1 + βP12
β decreases for higher mpΛ masses (expected due to lowerkaon momentum)α non zero for low mpΛ mass → extraction of spin tripletscattering length possible → publication in preparation
September 07, 2015 Florian Hauenstein Slide 12
Mem
berof
theHelmho
ltz-Associatio
n
Analyzing Power of Final State Particles
)CMSpθcos(
1 0.5 0 0.5 1
pro
ton
an
aly
zin
g p
ow
er
0.15
0.1
0.05
0
0.05
0.12.95 GeV/c [Jow14]
2.7 GeV/c
preliminary)
CMS
Λθcos(
1 0.5 0 0.5 1
an
aly
zin
g p
ow
er
Λ
0.2
0.15
0.1
0.05
0
0.05
0.1
0.152.95 GeV/c [Roe11]2.95 GeV/c [Jow14]2.75 GeV/c [Piz07]2.7 GeV/c
preliminary
)CMS
Kθcos(
1 0.5 0 0.5 1
ka
on
an
aly
zin
g p
ow
er
0.1
0
0.1
0.2
0.3
2.95 GeV/c [Roe11]
2.95 GeV/c [Jow14]
2.75 GeV/c [CTOF07,Piz07]
2.7 GeV/c
preliminary Proton and kaon analyzingpower: Same behavior fordifferent momentaΛ analyzing power: forcos(θCMS
Λ > 0) differentbehavior
September 07, 2015 Florian Hauenstein Slide 13
Mem
berof
theHelmho
ltz-Associatio
n
Λ PolarizationDetermination Principle
pBeam
scatteringplane
nsp = pBeam x pΛ
pp**
pπ**
pΛθ**
Λ polarization along nsp axisMeasurement via selfanalyzing Λ decayDistribution of decay protons:I = I0(1 + αPΛ cos θ∗∗)
α = 0.642± 0.013 (weakasymmetry parameter)Determination by "weightedsum method" [D. Besset et al., Nucl.
Instr. Meth. 166, 515 (1979)]
PΛ =1α
∑Ni=0 cos(θ
∗∗i )∑N
i=0 cos2(θ∗∗i )
September 07, 2015 Florian Hauenstein Slide 14
Mem
berof
theHelmho
ltz-Associatio
n
Results for the Λ Polarization
)CMS
Λθcos(
1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
ΛP
0.4
0.3
0.2
0.1
0
0.1
0.2
0.3
0.4
2.95 GeV/c [Roe11]
2.75 GeV/c [Piz07]
2.7 GeV/c
preliminary
[Roe11]M. Roeder, PhD Thesis,University Bochum, 2012
[Piz07]C. Pizzolotto, PhD Thesis,University Erlangen, 2007
2.7GeV/cHauenstein, PhD Thesis,University Erlangen, 2014
Λ polarization changes signFurther study by fitting of associated Legendre polynomials toavailable COSY-TOF data
September 07, 2015 Florian Hauenstein Slide 15
Mem
berof
theHelmho
ltz-Associatio
n
Λ PolarizationAssociated Legendre Polynomials Fits
)CMS
Λθcos(
1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
ΛP
0.4
0.3
0.2
0.1
0
0.1
0.2
0.3
0.4
)2
1 P• 2
+ C1
1 P• 1
fit (C
)θ (cos1
1 P• 1
C
)θ (cos2
1 P• 2
C
/ NDF = 1.982χ
0.008± = 0.002 1
C
0.006± = 0.133 2
C
2.7GeV/c
preliminary
)CMS
Λθcos(
1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
ΛP
0.2
0.1
0
0.1
0.2
0.3)
2
1 P• 2
+ C1
1 P• 1
fit (C
)θ (cos1
1 P• 1
C
)θ (cos2
1 P• 2
C
/ NDF = 0.792χ
0.036± = 0.013 1
C
0.027± = 0.030 2
C
2.75 GeV/c [Piz07]
preliminary
)CMS
Λθcos(
1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
ΛP
0.2
0.1
0
0.1
0.2
0.3
)2
1 P• 2
+ C1
1 P• 1
fit (C
)θ (cos1
1 P• 1
C
)θ (cos2
1 P• 2
C
/ NDF = 2.312χ
0.019± = 0.020 1
C
0.014± = 0.066 2
C
2.95 GeV/c [Roe11]
preliminary
)CMS
Λθcos(
1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1
ΛP
0.4
0.2
0
0.2
0.4
)2
1 P• 2
+ C1
1 P• 1
fit (C
)θ (cos1
1 P• 1
C
)θ (cos2
1 P• 2
C
/ NDF = 0.752χ
0.053± = 0.012 1
C
0.040± = 0.188 2
C
3.2 GeV/c [Schr03]
preliminary
September 07, 2015 Florian Hauenstein Slide 16
Mem
berof
theHelmho
ltz-Associatio
n
Λ PolarizationAssociated Legendre Polynomials Contributions
[GeV/c]beam
p2.7 2.8 2.9 3 3.1 3.2
mag
nit
ud
es [
arb
. u
nit
s]
2 a
nd
C1
C
0.2
0.1
0
0.1
0.2 1C
2C
preliminary
As expected C1 compatible with zero for all beam momentaC2 strong variation with beam momentum. Linear increase?No theoretical calculations available
September 07, 2015 Florian Hauenstein Slide 17
Mem
berof
theHelmho
ltz-Associatio
n
Summary
High statistics measurement with full phase space acceptance of the~pp → pKΛ reaction at 2.7GeV/c and 2.95GeV/cDalitz plot
Strong pΛ final state interactionStrength of enhancement at NΣ threshold (cusp effect) varieswith beam momentum
Scattering length at 2.7GeV/caeff = (−1.38+0.04
−0.05stat. ± 0.12syst. ± 0.3theo.) fm (preliminary)Kaon analyzing power: α not vanishing for low mpΛ massesFirst model independent determination of at possible
Λ analyzing powerDeviation for different beam momenta for cos θCMS
Λ > 0Λ polarization
Strong variation with beam momentumFit with Legendre polynomials → Solely described by P1
2September 07, 2015 Florian Hauenstein Slide 18
Mem
berof
theHelmho
ltz-Associatio
n
Outlook
Detailed study of the NΣ cusp effect at 2.95GeV/cCombined Partial Wave Analysis of pp → pKΛ at differentbeam momenta including data from DISTO and HADES/FOPIPublication of spin triplet scattering length at from pΛ finalstate interaction (September - October)Publication of polarization observables (PΛ,Ay ,DNN)→ Method paper submitted to NIM (arXiv:1508.04908)
September 07, 2015 Florian Hauenstein Slide 19
Mem
berof
theHelmho
ltz-Associatio
n
Backup Slides
September 07, 2015 Florian Hauenstein Slide 20
Mem
berof
theHelmho
ltz-Associatio
n
pΛ−NΣ Cusp
]2[GeV/cΛpM2 2.05 2.1 2.15 2.2 2.25 2.3
μ[Λp
/dM
σd
0
20
40
60
80
100
120
140 3.05GeV/cCOSY-TOF Coll., Eur. Phys. J. A49, 41 (2013)
Cusp described by Flattedistribution
Angular distributions in cuspregion point to S-wave inK − pΣ and subsequent Λ− p
In preparation: Study of cusp at2.95GeV/c
Reasonable description of spectrum byFSI + cusp(Flatte) + N∗ reflections
Further theoretical description necessary
/indfi2χ 226.8i/i163i
NΣg i0.180±1.253i
[GeV]irm i0.02±2.31i]i2[GeV0ΓC* i0.0241±0.3106i
]i-1[GeV0
c i0.0000334±0.0007869i]i2[GeV2c i0.001±3.713i
0a i0.08156±0.08079i
1a i0.00424±0.03065i
2a i0.0162±0.0115i
]i2[GeV/cΛinvariantimassip
2.05 2.1 2.15 2.2 2.25yi
eld
i[ar
b.iu
nit
s]
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6/indfi2χ 226.8i/i163i
NΣg i0.180±1.253i
[GeV]irm i0.02±2.31i]i2[GeV0ΓC* i0.0241±0.3106i
]i-1[GeV0
c i0.0000334±0.0007869i]i2[GeV2c i0.001±3.713i
0a i0.08156±0.08079i
1a i0.00424±0.03065i
2a i0.0162±0.0115i
2.95GeV/c
preliminarydσ
dmp
Λ/PS
Jowzaee, EPJA, in preparation
September 07, 2015 Florian Hauenstein Slide 21
Mem
berof
theHelmho
ltz-Associatio
n
Dalitz Plot Projections on mpΛ
]4/c2 [GeV2Λpm
4.2 4.3 4.4 4.5 4.6 4.7
)]4
/c2
b/(
GeV
µ [
2
Λp
/d m
σd
0
10
20
30 threshold
+Σn
threshold0
Σp
preliminary
2.7GeV/c
Hauenstein, PhD Thesis, 2014
2.95GeV/c
preliminaryJowzaee, PhD Thesis, 2014
Green: Scaled phase spacedistributionSmall enhancement at NΣthreshold
Brown: Scaled phase spacedistributionLarge enhancement at NΣthreshold compared to2.7GeV/c
September 07, 2015 Florian Hauenstein Slide 22
Mem
berof
theHelmho
ltz-Associatio
n
Effective pΛ Scattering Length for mKΛ Regionssee M. Roeder et al., Eur. Phys. J. A49, 157 (2013)
]4/c2 [GeV2Λpm
4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1
]4/c2
[G
eV2
ΛK
m
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
ΣN
N*
ΣK
upper regionlower region
2.95GeV/c
]2 [MeV/cΛpm2050 2060 2070 2080 2090 2100 2110
[ar
bit
rary
un
its]
2|M
|
0
1
2
3
4
5
6
7
8
9
10
all data
upper region +1.5 units
lower region +1.5 units
aeff = (−1.25± 0.08stat. ± 0.3theo.) fm(full data)aeff = (−2.06± 0.16stat. ± 0.3theo.) fm(upper region)aeff = (−0.86± 0.06stat. ± 0.3theo.) fm(lower region)
Strong influence of N∗ resonancesError in the order of 1 fm
September 07, 2015 Florian Hauenstein Slide 23
Mem
berof
theHelmho
ltz-Associatio
n
α Measurement at 2.95GeV/csee M. Roeder et al., Eur. Phys. J. A49, 157 (2013)
*)Kθ cos(-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
An
alys
ing
Po
wer
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
Associated Legendre Polys
0.013)± (-0.145 × 11P
0.010)± (0.065 × 12P
/NDF = 0.542χ
]2 [MeV/cp - mΛ - mΛp m0 20 40 60 80 100 120 140 160 180 200 220
coef
fici
ents
0
0.05
0.1
0.15
0.2
0.25
Unexpected: α is < 11% (3σ) for low invariant mass→ no sufficient precision for extraction of spin triplet pΛscattering lengthβ behavior reasonable
→ Work in progress: Analysis of additional measurement at2.95GeV/c to reduce statistical error
September 07, 2015 Florian Hauenstein Slide 24
Mem
berof
theHelmho
ltz-Associatio
n
Results from the Measurement at 2.7GeV/cDalitz Plot Slices
]4/c2 [GeV2Λp
m4.2 4.3 4.4 4.5 4.6 4.7
]4
/c2
[G
eV
2Λ
K
m
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
0
50
100
150
200
250
300
350
400
> 0.5Λp
pKθcos
]4/c2 [GeV2Λp
m4.2 4.3 4.4 4.5 4.6 4.7
]4
/c2
[G
eV
2Λ
K
m
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
0
50
100
150
200
250
300
350
400
> 0Λp
pKθ0.5 > cos
]4/c2 [GeV2Λp
m4.2 4.3 4.4 4.5 4.6 4.7
]4
/c2
[G
eV
2Λ
K
m
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
0
50
100
150
200
250
300
350
400
> 0.5Λp
pKθ0 > cos
]4/c2 [GeV2Λp
m4.2 4.3 4.4 4.5 4.6 4.7
]4
/c2
[G
eV
2Λ
K
m
2.6
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
0
50
100
150
200
250
300
350
400
< 0.5Λp
pKθcos
September 07, 2015 Florian Hauenstein Slide 25
Mem
berof
theHelmho
ltz-Associatio
n
Effective pΛ Scattering Length for Dalitz Plot SlicesLikelihood Distributions
a [fm]
1.55 1.5 1.45 1.4 1.35 1.3
lik
eli
ho
od
pro
ba
bil
ity
[a
rb.
un
its
]
0
2
4
6
constant 6.495
mean [fm] 1.407
sigma [fm] 0.037
> 0.5Λp
pKθcos
preliminarya [fm]
1.2 1.15 1.1 1.05
lik
eli
ho
od
pro
ba
bil
ity
[a
rb.
un
its
]
0
2
4
6
8 constant 7.635
mean [fm] 1.139
sigma [fm] 0.027
> 0Λp
pKθ0.5 > cos
preliminary
a [fm]
1.3 1.25 1.2 1.15 1.1
lik
eli
ho
od
pro
ba
bil
ity
[a
rb.
un
its
]
0
2
4
6
constant 6.861
mean [fm] 1.186
sigma [fm] 0.029
> 0.5Λp
pKθ0 > cos
preliminarya [fm]
1.3 1.25 1.2 1.15
lik
eli
ho
od
pro
ba
bil
ity
[a
rb.
un
its
]
0
2
4
6
constant 6.795
mean [fm] 1.244
sigma [fm] 0.025
< 0.5Λp
pKθcos
preliminarySeptember 07, 2015 Florian Hauenstein Slide 26
Mem
berof
theHelmho
ltz-Associatio
n
CMS Distributions for 2.7 GeV/c
1 0.5 0 0.5 1
b/s
r]
µ [
Ω / d
σ
d
0.5
1
CMSpθcos
1 0.5 0 0.5 1
RE
. [%
] •
AC
.
0
5
10
15
preliminary
p
1 0.5 0 0.5 1
b/s
r]
µ [
Ω / d
σ
d
0.5
1
CMSΛθcos
1 0.5 0 0.5 1
RE
. [%
] •
AC
.
0
5
10
15
preliminary
Λ
1 0.5 0 0.5 1
b/s
r]
µ [
Ω / d
σ
d
0.5
1
CMS
Kθcos
1 0.5 0 0.5 1
RE
. [%
] •
AC
.
0
5
10
15
preliminary
KDistributions almostsymmetricSmall deviations at boardersdue to acceptance correction
September 07, 2015 Florian Hauenstein Slide 27
Mem
berof
theHelmho
ltz-Associatio
n
Formulas for Scattering Length Extraction
Parametrization of pΛ invariant mass spectrum
dσdmpΛ
= PS · |AFSI(mpΛ)|2 = PS ·exp
[C0 +
C1
m2pΛ − C2
]. (1)
a dependence on C1 and C2
at(C1,C2) = −~c2C1 ×
√(m2
0mpmΛ
)(m2
max −m20)
(m2max − C2)(m2
0 − C2)3
with m0 = mp + mΛ and mmax = m0 + 40MeV/c2
Spin Triplet Amplitude
|At(mpΛ)|2 = −α ·∣∣∣Aeff(mpΛ)
∣∣∣2September 07, 2015 Florian Hauenstein Slide 28
Mem
berof
theHelmho
ltz-Associatio
n
Analyzing PowerDetermination Principle
Angular distribution for particles with polarization PY :( dσdΩ )pol. = ( dσ
dΩ )0 · (1 + ANPN) = ( dσdΩ )0 · (1 + ANPY cosφ)
L
RPY AN
AN(cos θCMS) =εLR(cos θCMS, φ)
cos(φ) · pB
Azimuthal left-right asymmetry
εLR(cos θCMS, φ) =L(θCMS
p ,φ)−R(θCMSp ,φ)
L(θCMSp ,φ)+R(θCMS
p ,φ)
Count ratesL(θCMS
p , φ)) =√N+(φ) · N−(φ+ π) and
R(θCMSp , φ) =
√N+(φ+ π) · N−(φ)
Beam polarization pB
September 07, 2015 Florian Hauenstein Slide 29
Mem
berof
theHelmho
ltz-Associatio
n
Experimental SetupStraw Tube Tracker (STT)
2704 straw tubes (l = 1m, d = 1 cm)arranged in 13 double layers
Every double layer is shifted by 60 angle tothe other for 3D track reconstruction
Ar : CO2 gas mixture with ratio 8 : 2 at1.2 bar overpressure
Drift time information used for track to wiredistance
Obtained averaged spatial resolutionσ = (137± 9) µm
September 07, 2015 Florian Hauenstein Slide 30
Mem
berof
theHelmho
ltz-Associatio
n
Event ReconstructionSteps for pp → pKΛ reconstruction
1 Track finding (Hough transformation) and fitting2 Vertex finding and fitting3 Geometric fit of pp → pKΛ event topology4 Kinematic fit of pp → pKΛ→ Kinematically complete events→ pΛ mass resolution σ = 1.1MeV/c2
u’ [cm]30 20 10 0 10 20 30
z [
cm
]
0
10
20
30
40
50
60
v’ [cm]30 20 10 0 10 20 30
z [
cm
]
0
10
20
30
40
50
60
w’ [cm]30 20 10 0 10 20 30
z [
cm
]
0
10
20
30
40
50
60
September 07, 2015 Florian Hauenstein Slide 31
Mem
berof
theHelmho
ltz-Associatio
n
Event Selection
Selection criteriaχ2kin.fit < 5
Λ decay length > 3 cm](Λ, decayproton) > 2
Monte Carlo simulationsLow background from otherreactions (pp → pKΣ0 < 1%)Reconstruction efficiency∼ 15%
/ NDFK
2χ0 2 4 6 8 10
arb
itra
ry u
nit
s310
410
510
ΛpK
0ΣpK
Missing Energy [MeV]100 80 60 40 20 0 20 40 60 80 100
En
trie
s / B
in
0
5000
10000
15000
20000
25000
30000all selections
/ NDF < 50K
2χ
September 07, 2015 Florian Hauenstein Slide 32
Mem
berof
theHelmho
ltz-Associatio
n
Future of COSY
Test facility for FAIR (Facility for Antiproton and Ion Research) atGSI in Darmstadt, Germany
Accelerator components → HESR at FAIRDetector components → PANDA, CBM, ...
Measurement of charged particle EDM (Electric Dipole Moment)
EDMs are candidates to solvematter-antimatter asymmetry
Measurement of proton and deuteron EDMwith one dedicated ring → JEDI collaboration
Precursor experiments with actual COSY ring
September 07, 2015 Florian Hauenstein Slide 33
Mem
berof
theHelmho
ltz-Associatio
n
Spin Triplet Scattering Length atPreliminary from Hauenstein, PhD Thesis, 2014
/ ndf 2χ 73.43 / 36
p0 0.0432± 0.1482
p1 1.135e+04± 1.318e+05
p2 5.202e+03± 4.151e+06
]2 [MeV/cΛp m
2060 2080 2100 2120 2140 2160
)]2
[n
b/(
MeV
/cΛ
p
/d m
σd
0
50
100
/ ndf 2χ 73.43 / 36
p0 0.0432± 0.1482
p1 1.135e+04± 1.318e+05
p2 5.202e+03± 4.151e+06
/ ndf 2χ 73.43 / 36
p0 0.0432± 0.1482
p1 1.135e+04± 1.318e+05
p2 5.202e+03± 4.151e+06
preliminary
/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06
]2 [MeV/cΛp m
2060 2080 2100 2120 2140 2160
) [a
rb. u
nit
s]
Λp
(m
Kα
*
Λp
/d
mσ
d
0
10
20
/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06
/ ndf 2χ 9.086 / 5p0 0.2730± 0.7746 p1 4.625e+04± 4.931e+04 p2 3.276e+04± 4.186e+06
preliminary
fit limit
Rebin
×(−αK )
Parametrization: dσdmpΛ
= Phasespace · exp[p0 + p1
m2pΛ−p2
]at = (−1.31+0.32
−0.49stat. ± 0.3theo. ± 0.16syst.) fm (very preliminary)
First direct determination of atComparison:
at = (−1.6+1.1−0.8) fm (Λp elastic scattering)
at = −1.54 fm (theoretical calculation [NPA 915, 24-58 (2013)])September 07, 2015 Florian Hauenstein Slide 34