Production and Dalitz decays of baryon resonances in p+p … · Production and Dalitz decays of...
Transcript of Production and Dalitz decays of baryon resonances in p+p … · Production and Dalitz decays of...
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Production and Dalitz decays of baryon resonances
in p+p interactions at Ekin=1.25 and 3.5 GeV
beam energy with HADES
Witold Przygoda, Jagiellonian University
for the HADES Collaboration
18 June 2013
MESON NET Meeting 2013 17-19 June 2013, Prague, Czech Republic
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The HADES Spectrometer
Side View
START
FW
1 m
RPC (from 2010)
ϕ: full, θ: 18 - 85 e+e- pair acceptance 0.35 ~80.000 channels, segmented solid or LH2 target
SIS18 beam: π, p, A
Δm/m ~ 2-3% at /
Versatile detector for rare particle decays :
• dielectrons (e+, e-)
• strangeness: , K,0 , -
• upgrade(2010): new DAQ (20 KHz), Tof-RPC (tof ~80 ps) 2
G. Agakichiev et al. Eur. Phys. J. A41 (2009) 243
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p+p @ 1.25 GeV - plan
𝒑 + 𝒑 elementary reactions at E = 1.25 GeV below production threshold
are well situated to investigate
Δ(1232) Dalitz decay
I. HADRON ANALYSIS (npπ+, ppπ0)
II. LEPTON ANALYSIS (ppe+e-, ppe+e-)
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𝑝 + 𝑝
𝑝∆+ 𝑝∆++
𝑝𝒏𝝅+ 𝑝𝒑𝝅𝟎 𝑛𝒑𝝅+
𝑝𝒑𝒆+𝒆−
𝑝𝑝𝒆+𝒆−𝜸
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Resonance model Production: OPEM
Λ𝜋 fitted in accordance with the data (𝛬𝜋 = 0.75) V. Dmitriev et al. Nucl. Phys. A459
(1986) 503
Form factor at vertices:
𝐹 𝑞2 =Λ𝜋
2 − 𝑚𝜋2
Λ𝜋2 − 𝑞2
Z. Teis et al., Z. Phys. A356 (1997) 421
4 Witold Przygoda (MESONNET 2013)
G. A
gaki
shie
v et
al.
Eur.
Ph
ys. J
. A 4
8 (
20
12
) 7
4
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production (n p π+)
Witold Przygoda (MESONNET 2013) 5
black line – total red line – Δ++(1232) green line – Δ+(1232) blue line – N(1440) yellow – phasespace
in acceptance
OPEM (𝛬𝜋 = 0.75 modified) Δ resonance + FSI + N(1440) small
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production (n p π+) - 4π corrected
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grey band:
correction with various OPEM parametrisations (𝛬𝜋 = 0.63, 0.75, 1.00)
cross section:
17.5 ± 0.5 mb
”symmetrized”
ACC corrected
2-dim correction matrix:
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production (p p π0)
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Identifying 2 protons • strongly reduces acceptance • amplifies large 4-mom transfer
parametrisation deduced from the npπ+ channel
in acceptance
black line – total red line – Δ+(1232) blue line – N(1440) yellow – phasespace
red line – Δ+(1232)+N(1440) blue line – N(1440)
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production (p p π0) - 4π corrected
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ACCEPTANCE corrected
”fiducial volume” in angular distribution i.e. -0.6 < cos θ < +0.6
cross section:
see dilepton analysis (next slides)
Acceptance correction:
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QED
cloud/core ~ 0.44/0.56
Mee [GeV/c2]
QED
cloud/core ~ 0.99/0.01
M=1.23 M=1.5
M=1.8
Δ Ne+e-
22
2
2
2222
232, qqqΔf Gm
qGGqm C
Δ
EM2
-
dq
)eNe(Δd
M.I. Krivoruchenko et al. Phys. Rev. D65 (2002) 017502
Q. Wann, F. Iachello Int. J. Mod. Phys. A20 (2005) 1846
G. Ramalho, M. T. Peña Phys. Rev. D85 (2012) 113014
Time Like (q2 >0)
(J=3/2) ->N (J=1/2) * transition:
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q q q
quark core
e+
e-
e-
pion cloud
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+ identification via pp 0 { e+e- }
black – pp analysis blue – ppee analysis
ACC corrected
both channels with 2 protons (pp and ppe+e-) support the description of angular distribution according to OPE (modified) with parameter Λ𝜋 = 0.75 Cross section deduced (blue points) 4.25 0.5 mb
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E.L.Bratkovskaya et al. Phys. Lett. B348, 283 (1995)
𝜋0 helicity
ACC corrected
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+ Dalitz decay via pn+ { pe+e- }
M.I. Krivoruchenko et al. Phys. Rev. D65, 017502 (2002)
form-factors – Very important at higher energy!
Dalitz decay BR
GM(0)~3 GE(0)~0 GC(0)~0
missing mass selection
Mee > 0.15 SIGNAL: 200, CB: 15
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red line – total black – π0 Dalitz blue line – Δ Dalitz grey band – (VMD)
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(pee) angular observables, BR
BR = 𝑁
∆ → 𝑝𝑒+𝑒−
𝑁∆ → 𝑝𝜋0
derived in the ”fiducial area” −0.7 < cos 𝜃𝑝𝑒𝑒
𝐶𝑀 < 0.7
BR = 4.42 10-5 20% (syst.) 9% (stat.)
helicity in agreement with QED
1 + 𝐴 ∙ cos2𝜃 (when neglecting Gc(q) at small q
2)
preliminary
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preliminary
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p+p @ 3. 5 GeV - plan
𝒑 + 𝒑 elementary reactions at E = 3.5 GeV to investigate the wealth of baryionic resonances
and their properties
I. HADRON ANALYSIS (npπ+, ppπ0)
II. LEPTON ANALYSIS (ppe+e-)
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Inclusive e+e- spectrum p+p @ 3.5 GeV
How to treat R N e+e- • mesons produced via baryonic
resonances (R ρ N e+ e- N) • Resonance model with eTFF from model
seems to describe nicely data – only Δ?
J. Weil et al. (GiBUU) Eur. Phys. J. A48 (2012) 111
arxiv.org/abs/1305.3118
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G. Agakishiev et al. Eur. Phys. J. A 48 (2012) 64
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Baryon resonances in p+p @ 3. 5 GeV
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Resonance model:
production amplitude given by incoherent sum of
resonance contributions, isospin relations
Starting point: S. Teis R parametrization (S. Teis et al., Z. Phys. A356, 421 (1997).),
take 4* resonances + empirical angular distributions
(strong forward-backward peaking)
)()(
MR t
AM
dt
d
Study of 3 connected exclusive channels: • pppp0 and pppn+ to fix R (,N*) cross sections
• Convert Rpe+e- and check in pp ppe+e-
BR(Rpe+e-) : „QED” point-like R-* vertex
M. Zetenyi and Gy. Wolf., Heavy Ion Phys. 17 (2003) 27.
For the overlaping resonances only one
resonance with largest BR(N) selected
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Resonance production (HADES acceptance)
Witold Przygoda (MESONNET 2013) 16 P.Salabura
)()(
MR t
AM
dt
d
n p π+
extension of angular parametrisation as a function of t for all resonances
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One pion production: acceptance corrected
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n p π+
p p π0
• ++ (1232) dominant excelent description of -line
shape („Monitz” FF)
• +(1232), N*(1440),N*(1520),..
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Exclusive / production in p+p @ 3. 5 GeV
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=
=
pp = ½ · pp
N* (1535) fixed from Dalitz plot
N* (1535) ->p BR(42%)
N*(1535) = 1520.15 [mb]
K. Teilab (PhD Thesis) Univ. Frankfurt (2011)
F. Balestra et al. (DISTO) Phys. Rev. Lett. 89 (2002) 092001
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Exclusive p+p @ 3.5 GeV (dileptons) 1
no off shell coupling to VM lower limit for e+e- emission experimental for / used missing yield related to low mass resonances
„QED”
point-like RN* vertex
M. Zetenyi, G. Wolf Phys. Rev. C67 (2003) 044002
preliminary
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Exclusive p+p @ 3.5 GeV (dileptons) 2
no free / production missing yield related to high mass resonances !
M. I. Krivoruchenko, B.V. Martemyanov
Ann. Phys. 296 (2002) 299
extended VDM
preliminary
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Exclusive p+p @ 3.5 GeV (dileptons) 3
saturation - what about higher resonances?
Δ modification
preliminary
„QED” point-like RN* vertex
+ eTTF Δ(1232) Wan / Iachello
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CREDITS
𝑻𝒉𝒆 𝑯𝑨𝑫𝑬𝑺 𝑪𝒐𝒍𝒍𝒂𝒃𝒐𝒓𝒂𝒕𝒊𝒐𝒏
Piotr Salabura (spokesperson)
me Manuel Lorenz
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Gosia Gumberidze
Adrian Dybczak
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BACKUP SLIDES
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Normalization – pp elastic
EDDA experiment 46-135⁰ in CM cross section
3.99 0.23 mb
normalization error 7.5%
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Partial Wave Analysis proton+proton (isospin I = 1) S – spin, L – orbital momentum, J – total angular momentum
INITIAL PP STATES (-1)S+L+I = -1
for S=0: L even… L=0 (J=0) or L=2 (J=2)… for S=1: L odd… L=1(J=0,1,2) or L=3 (J=2,3,4)…
FINAL STATES S-, P-, D-waves in pp or pn-state P33(1232) and P11(1440) in πN state
J I = 1
0 1S0, 3P0
1 3P1
2 1D2, (3P2,
3F2)
3 3F3
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K.N. Ermakov et al. Eur. Phys. J. A47 (2011) 159
Motivation:
Formalism: Andrey Sarantsev talk
(which was on Tuesday)
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Input for PWA – other data
Experimental data samples
1628 MeV/c 1760 ± 60 µb 2912
π+ p n
Bonn-Gatchina group http://pwa.hiskp.uni-bonn.de/data.htm
Proton Momentum
Total cross section
Data (events)
950 MeV/c 1217 MeV/c 1279 MeV/c 1341 MeV/c 1389 MeV/c 1437 MeV/c 1485 MeV/c 1536 MeV/c 1581 MeV/c 1628 MeV/c 1683 MeV/c
100 ± 30 µb 2070 ± 90 µb 2850 ± 130 µb 3310 ±190 µb 3700 ± 140 µb 3730 ± 150 µb 3960 ± 150 µb 4200 ± 150 µb 4190 ± 170 µb 4480 ± 200 µb 4500 ± 170 µb
154972 542 615 882 993 914 996 1315 903 688 1086
Proton Momentum
Total cross section
Data (events)
π0 p p
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PWA solutions
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• several solutions tested • with HADES data only • with all experimental data sets • with resonances Δ and N* only • with / without resonance N* • with / without 3F3 input pw
• systematic tests on missing mass cut • systematic tests on background (Q-factor)
two examples
good data description in various projections but cross sections not
worse data description in some projections but cross sections quite good
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PWA (n p π+) – in acceptance
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black line – total red line – P33(1232) blue line – P11(1440)
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PWA (n p π+) – in acceptance
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PWA (p p π0) – in acceptance
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PWA (n p π+) – 4π black line – total red line – P33(1232) blue line – P11(1440)
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PWA (n p π+) – 4π
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PWA (p p π0) – 4π
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PWA (n p π+) – in acceptance
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black line – total red line – P33(1232) blue line – P11(1440)
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PWA (n p π+) – in acceptance
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PWA (p p π0) – in acceptance
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PWA solutions
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n p π+ (17.5 ± 1 mb ) p p π0 (4.3 ± 0.5 mb)
cross section [mb] 14.7 16.9 5.1 4.5
P33(1232) in 4π 61% 60% 74% 93%
P33(1232) in acceptance 50% 66% 88% 105%
P11(1440) in 4π 17% 16% 55% 57%
P11(1440) in acceptance 21% 22% 54% 63%
input partial waves n p π+ p p π0
1S0 3% 12% 8% 10%
1D2 8% 8% 8% 5%
3P0 7% 13% 6% 8%
3P1 27% 29% 15% 18%
3P2 38% 38% 70% 68%
3F2 18% 21% 17% 18%
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PWA solutions
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input partial wave output (n p π+) output (p p π0)
1S0 2-8% 1S0 P11(1440)-p 1S 3-10% 1S0 P11(1440)-p 1S
1D2 3-6% 1D2 P33(1232)-p 5D 4-8% 1D2 P33(1232)-p 5D
3P0 4-5% 3P0 (pp)(3P1)pi 3P 17-30% 3P0 (pp)(3P1)pi 3P
4-8% 3P0 P11(1440)-p 3P 14-32% 3P0 P11(1440)-p 3P
3P1 8-16% 3P1 P33(1232)-p 3P 10-18% 3P1 P33(1232)-p 3P
0-3% 3P1 (pp)(3P2)pi 5P 0-7% 3P1 (pp)(3P2)pi 5P
3P2 29-36% 3P2 P33(1232)-p 3P 61-75% 3P2 P33(1232)-p 3P
5-14% 3P2 P11(1440)-p 3P 15-33% 3P2 P11(1440)-p 3P
3F2 13-15% (pn)(1P1)pi 3P 20-28% P33(1232)-p 5P
1-2% (pp)(3P1)pi 3P 10% (pp)(3P1)pi 3P
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Comparison (4π) PWA and data
Legend: (red line) OPE modified (𝛬𝜋 = 0.75)
(blue line) PWA – resonance P33(1232)
(dashed black) PWA total
(dashed blue) – resonance P11(1440)
n p π+
PWA Δ++ in 4π 61% of total
PWA up-scaled
the same 𝑑𝜎
𝑑𝑀 of Δ++ in the pole
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Comparison (4π) PWA and data
Legend: (red line) OPE modified (𝛬𝜋 = 0.75)
(blue line) PWA – resonance P33(1232)
(dashed black) PWA total
(dashed blue) – resonance P11(1440)
p p π0
PWA Δ+ in 4π 74% of total
PWA the same scale
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