Search for the LHCb Charmed Pentaquark in Photo …...Oct 26, 2018 · Quasi-real production H1 and...
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Search for the LHCb Charmed Pentaquark in Photo-production at Hall C Sylvester Joosten J/ψ-007 Collaboration Meeting, October 2018
Transcript of Search for the LHCb Charmed Pentaquark in Photo …...Oct 26, 2018 · Quasi-real production H1 and...
Search for the LHCb Charmed Pentaquark
in Photo-production at Hall C
Sylvester Joosten
J/ψ-007 Collaboration Meeting, October 2018
S. Joosten
The LHCb charmed “pentaquark” Pc: still a hot topic!
Slide from PAC talk (2016) Today: 579 citations
~200 citations/year for 2.9 years
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S. Joosten
Discovery of the LHCb charmed “pentaquark” Pc
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⇤b ! ⇤⇤J/ ! (K�p)J/
⇤b ! K�Pc ! K�(pJ/ )
⇤b ! K�pJ/ Aaij, R, et. al (LHCb) PRL 115-7 (2015)
wide: Pc(4390) (9σ)
2 Pc states needed to describe results
narrow: Pc(4450) wide: Pc(4380)
spin/parity either: 5/2+, 3/2- (most likely!) 5/2-, 3/2+ 3/2-, 5/2+
narrow: Pc(4450) (12 σ)
S. Joosten
charmed “pentaquark” in photo-production
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Possible explanations for LHCb observations: LHCb: 2 new charmed “pentaquark” (Pc) states alternative: kinematic enhancements through anomalous triangle singularity (ATS)
Photo-production ideal tool to distinguish between both explanations
if Pc real states, also created in photo-production kinematic enhancement through ATS not possible
Pc(4450) translates to narrow peak around Eγ = 10 GeV
Lui X-H, et al., PLB 757 (2016), p231 (and references therein)
Wang Q., et al., PRD 92-3 (2015) 034022-7 (and references therein)
JLab perfect place for this measurement!
S. Joosten 5
J/ψ photo-production: Direct photo-production Cornell ’75, SLAC ’75, CERN NA-14, FNAL E401, E687 Quasi-real production H1 and ZEUS Ultra-peripheral collisions LHCb ’14 (pp) and ALICE ’15 (pPb)
J/ψ photo-production: what do we know?
Well constrained above W > 15 GeV Dominated by t-channel 2-gluon exchange
Almost no data near threshold
γ,γ*J/ψ,Υ
l -
l+
p p’
q
q_
10 210 310W (GeV)
3−10
2−10
1−10
1
10
210
310
(nb)
ψJ/σ
Cornell '75SLAC '75CERN NA-14FNAL E401FNAL E687
*)γH1 Combined (*)γZEUS Combined (
LHCB '14 (UPC)
J/ψ
S. Joosten 6
Why the threshold region?
Near Threshold: Origin of proton mass, trace anomaly of the QCD energy-momentum tensor. Gluonic Van der Waals force, possible quarkonium-nucleon/nucleus bound states Mechanism for quarkonium production
10 210 310W (GeV)
3−10
2−10
1−10
1
10
210
310
(nb)
ψJ/σ
Cornell '75SLAC '75CERN NA-14FNAL E401FNAL E687
*)γH1 Combined (*)γZEUS Combined (
LHCB '14 (UPC)
J/ψ
[GeV]γE10 15 20
[nb]
σ
2−10
1−10
1
10
210
310Cornell 75
SLAC 75
SLAC 76 (Unpub.)
2-gluon fit
Pc?
LHCb charmed (charming) pentaquark
S. Joosten 7
S.J. Brodsky, et al., Phys.Lett. B498, 23-28 (2001)
Same as high energies (2-gluon)?
2-gluon 3-gluon
Production mechanism near threshold unknown
Or a partonic soft mechanism (power law 2-gluon form-factor)?
Frankfurt and Strikman., PRD66 (2002), 031502
partonic soft
Orders of magnitude difference 2-gluon fastest drop-off
Drives required luminosity for threshold measurement
Maybe 3-gluon exchange dominant?
S. Joosten
2-gluon fit near threshold
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10 15 20 25 (GeV)γE
4−10
3−10
2−10
1−10
1
10
210
310
(nb)
ψJ/
σ
Cornell '75
SLAC '75
SLAC '76 (Unpublished)
2-gluon fit
J/ψ
Smallest cross section drives required precision and luminosity Use 2-gluon estimate for experimental projections near threshold
S. Joosten
Resonant J/ψ production through Pc decay
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[GeV]γE8 8.5 9 9.5 10 10.5 11 11.5 12
[nb]
σ
0
0.2
0.4
0.6
0.8
1Cornell 75
SLAC 76 (Unpublished)
t-channel (2-gluon)
5/2+ (3% coupling)cP
3/2- (3% coupling)cP
sum
)θcos(1− 0.8− 0.6− 0.4− 0.2− 0 0.2 0.4 0.6 0.8 1
Arbi
trary
Uni
ts
0
1
2
3
4Ψt-channel J/
5/2+cP 3/2-cP 5/2-cP 3/2+cP
Cross section depends on coupling to (J/ψ, p) channel J/ψ angular distribution depends on Pc spin/parity
P c
s − channel
γ J/ ψ
(a)
P c
u − channel
γ J/ ψ
(b)P’P
P P’
s-channel u-channel
Leverage cos(θ) dependence to maximize S/B at low coupling!
d�
d cos ✓J/ (�p ! Pc ! J/ p)
3% coupling
Wang Q., et al., PRD 92-3 (2015) 034022-7
S. Joosten 10
To beamdump
1
3
D
Q
Incidentbeam
Hydrogentarget
e-
Detector Stacks:Tracking/ Timing:
1. Drift Chambers2. Hodoscopes
3. Gas erenkov4. Lead Glass Calorimeter
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4
Particle ID:
9% Cu Radiator
D
QSHMS
HB
Argon/Neon Cerenkov
HGC
S1XS1Y
AGC
DC1
DC2
S2XS2Y LGC
A1
C4F10 Cerenkov
1 22
3
1
4
HMS
e+
Run with 2 settings: ”SIGNAL” Setting (9 days): minimizes accidentals and maximizes signal/background:
HMS: 34o, 3.25 GeV electrons SHMS: 13o, 4.5 GeV positrons
”BACKGROUND” Setting: (2 days): precise determination of the t-channel background
HMS: 20o, 4.75 GeV electrons SHMS: 20o, 4.25 GeV positrons
Setup similar to E-05-101(WACS) 50μA electron beam at 11GeV 10.6 GeV 9% copper radiator 15cm 10cm LH2 total 10% RL
electron in HMS
positron in SHMS
J/ �
High-impact experiment …will run February 2019!
Pentaquark search E12-16-007 in Hall C
S. Joosten
Photon Energy Reconstruction
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Can unambiguously reconstruct the initial photon energy from the reconstructed J/ψ momentum and energy Assumptions:
photon beam along the z-axis proton target at rest 2 final state particles: a proton and a J/ψ
E� =M2 � 2EJMP
2(E �Mp � P cos ✓ )<latexit sha1_base64="wFhYCc1s5gP4TVZhwu/75FQTu0E=">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</latexit><latexit sha1_base64="wFhYCc1s5gP4TVZhwu/75FQTu0E=">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</latexit><latexit sha1_base64="wFhYCc1s5gP4TVZhwu/75FQTu0E=">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</latexit><latexit sha1_base64="wFhYCc1s5gP4TVZhwu/75FQTu0E=">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</latexit>
S. Joosten
Maximizing the sensitivity
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t-channel
Pc(4450) 5/2+
Use HMS and SHMS to maximize Pc signal over t-channel background
)θcos(1− 0.8− 0.6− 0.4− 0.2− 0 0.2 0.4 0.6 0.8 1
Arbi
trary
Uni
ts
0
1
2
3
4Ψt-channel J/
5/2+cP 3/2-cP 5/2-cP 3/2+cP
“SIGNAL” Setting
positron in SHMS
electron in HMS
S. Joosten
Resolution
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[GeV]γE9 9.5 10 10.5 11 11.5 12
Cou
nts
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100
200
300
Ψt-channel J/
3/2- (5.0% coupling)cP
5/2+ (5.0% coupling)cP
sum
[GeV]γE9 9.5 10 10.5 11 11.5 12
Cou
nts
0
100
200
Ψt-channel J/
3/2- (5.0% coupling)cP
5/2+ (5.0% coupling)cP
sum
Generated Reconstructed
[GeV]-e+eM3 3.02 3.04 3.06 3.08 3.1 3.12 3.14 3.16 3.18 3.2
Arbi
trary
Uni
ts
0
2
4
6
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reconstructed J/ψ mass: σ = 5 MeV
S. Joosten
[GeV]γE9 9.5 10 10.5 11 11.5 12
Cou
nts
0
50
100
150Ψt-channel J/
3/2- (5.0% coupling)cP 5/2+ (5.0% coupling)cP
sum2 day estimate
BACKGROUND (2 days)
t-channel: 682 events 5/2+: 204 events 3/2-: 26 events
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Projected results for “BACKGROUND” Setting
assuming 5% coupling value favored by existing photo-production data
(Corresponds to <1% coupling in V. Kubarovsky’s model)
2 days of beam time at 50μA able to separate 5/2+ from t-channel at low Eγ
Only 2 days!
]2t [GeV
6− 5− 4− 3− 2− 1− 0 1 2
Cou
nts
0
100
200
300 Ψt-channel J/ 3/2- (5.0% coupling)cP 5/2+ (5.0% coupling)cP
sum2 day estimate
First high-precision absolute cross section measurement near threshold!
Wang Q., et al., PRD 92-3 (2015) 034022-7
V. Kubarovsky, et al., PRD 92-3 (2015) 031502-4
J/ �
S. Joosten
Projected results for “SIGNAL” Setting
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]2t [GeV
6− 5− 4− 3− 2− 1− 0 1 2
Cou
nts
0
50
100
150
200
Ψt-channel J/ 3/2- (5.0% coupling)cP 5/2+ (5.0% coupling)cP
sum9 day estimate
assuming 5% coupling value favored by existing photo-production data
(Corresponds to <1% coupling in V. Kubarovsky’s model)
9 days of beam time 5/2+ peak dominates the spectrum 26x reduction in t-channel background rate
Only 9 days!
Wang Q., et al., PRD 92-3 (2015) 034022-7
Significance > 20σ!
V. Kubarovsky, et al., PRD 92-3 (2015) 031502-4
[GeV]γE9 9.5 10 10.5 11 11.5 12
Cou
nts
0
100
200
Ψt-channel J/ 3/2- (5.0% coupling)cP 5/2+ (5.0% coupling)cP
sum9 day estimate
SIGNAL (9 days) t-channel: 120 events
5/2+: 881 events 3/2-: 266 events
J/ �
S. Joosten
Sensitivity for Discovery
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coupling [%]1 1.5 2 2.5 3
]σ
Sens
itivi
ty [n
1
10
Projected Sensitivity
limitσ5
sensitivity calculated using a Δ-log-likelihood formalism 5 standard deviation level of sensitivity starting from 1.3% coupling!
What changed since the proposal?
S. Joosten
Changes since the proposal
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10.6GeV beam instead of 11GeV beam 10cm LH2 target instead of 15cm LH2 target Smaller SHMS momentum acceptance Needed to re-tune the settings!
#1 is signal setting #2 is the original t-channel background setting #3 is a new background t-channel setting
P HMS Theta HMS P SHMS Theta SHMS#1: -3.45 32.8deg. 4.35 13.6deg.#2: -4.75 20.0deg. 4.25 20.0deg.#3: -4.95 18.6deg. 4.95 16.7deg.
S. Joosten
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5coupling [%]
1
10
]σ
Sens
itivi
ty [n
Projected Sensitivity
limitσ5
Impact on sensitivity
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1 1.5 2 2.5 3 3.5 4 4.5 5 5.5coupling [%]
1
10
]σ
Sens
itivi
ty [n
Projected Sensitivity
limitσ5
Significant loss in statistics From 5 sigma at 1.3% to 5 sigma at 1.7%
PAC NEW
S. Joosten
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5coupling [%]
1
10
]σ
Sens
itivi
ty [n
Projected Sensitivity
limitσ5
Sensitivity assuming different models
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Wang et al. Kubarovsky et al
0.2 0.4 0.6 0.8 1 1.2 1.4coupling [%]
1
10
]σ
Sens
itivi
ty [n
Projected Sensitivity (Kubarovsky)
limitσ5
Situation improved when using Kubarovsky’s model!
S. Joosten
Projected results (5% coupling)
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8 8.5 9 9.5 10 10.5 11 11.5 12 [GeV]γE
1−10
1
10
[nb]
σ
"SIGNAL" Setting (15 days)"BACKGROUND" Setting 1 (4 days)"BACKGROUND" Setting 2 (2 shifts)Cornell 75SLAC 76 (Unpublished)
with Pc (5% coupling)ψJ/
8 8.5 9 9.5 10 10.5 11 11.5 12 [GeV]γE
1−10
1
10
[nb]
σ
"SIGNAL" Setting (18 days)"BACKGROUND" Setting (4 days)Cornell 75SLAC 76 (Unpublished)
(5% coupling)c with PψJ/
PAC NEW
S. Joosten
Summary
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High impact result will either confirm Pc resonance, or strongly exclude its existence
Strong sensitivity to the coupling down to 1.3% Will provide knowledge about J/ψ production (absolute cross section!) near threshold
Helps future experimental endeavors at CLAS12 and SoLID
Straightforward experiment, will run February 2019!
J/ �
