Talk QWG 2019 - agenda.infn.it
Transcript of Talk QWG 2019 - agenda.infn.it
PERSPECTIVES OF HADRONSPECTROSCOPY AT LHCb
[ARXIV:1808.08865]
Marco PappagalloUniversity of Edinburgh
On behalf of the LHCb Collaboration
QWG 2019 – The 13th International Workshop on Heavy Quarkonium17 May 2019, Turin, Italy
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SPECTROSCOPY AT LHCb
PRL 114 (2015) 062004
PRL 109 (2012) 172003
Λb**
Ξb** Ξcc++
PRL 119 (2017) 112001
PRL 112 (2014) 222002PRD 92 (2015) 112009
Zc(4430)+
LHCb has largely contributed to populate the zoo of particles. Some of them have a clear “exotic” signature
STANDARD
EXOTIC
PRL 115 (2015) 072001arXiv:1904.03947
Pc(4450)+
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SPECTROSCOPY AT LHCb
) [MeV]-K+cX(m3000 3100 3200 3300
Can
dida
tes /
(1 M
eV)
0
100
200
300
400 LHCb-K+cX
Full fitBackgroundFeed-downs
sidebands+cX
PRD 92 (2015) 011102PRL 110 (2013) 222001
PRL 118 (2017) 182001
Ωc**(?)
X(3872)PRL 114 (2015) 062004
PRL 109 (2012) 172003
PRL 119 (2017) 112001
Zc(4430)+
PRL 118 (2017) 022003PRD 95 (2017) 012002
X(4140)
STANDARD
EXOTIC
…but many other states have uncertain nature. Goal of the upcoming years is to probe their conventional/exotic nature…and find new candidates of course
Λb**
Ξb** Ξcc++
PRL 112 222002 (2014)PRD 92 112009 (2015)
PRL 115 (2015) 072001arXiv:1904.03947
Pc(4450)+
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LHCb GOING TO UPGRADE
Ø Main limitation that prevents exploiting higher luminosity with the present detector is the Level-0 (hardware) triggerü Level-0 output rate < 1 MHz (readout rate) requires raising thresholds
Ø This is particularly problematic for hadronic final statesØ Running at 2x1033 cm-2 s-1 with full software trigger, running at 40 MHz
Upgrade I ( Approved)
To be installed in Long Shutdown 4 of the LHC:Ø Subsystems redesigned to operate at a luminosity of 1-2 x 1034 cm-2 s-1
Ø Integrated luminosity of > 300 fb -1
Ø Extension of the experiment’s capabilities into selecting π0, η and low-momentumtracks
Upgrade II (Under approval)
Upgrade Ia Upgrade Ib Upgrade II
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PRL 119 (2017) 112001 PRL 121 (2018) 052002
DOUBLY HEAVY BARYONS
Ø Observations of Ξcc+ and Ωcc+ expected with RUN II data or during the upcoming Upgrade I
Ø Upgrade II will be useful into studying their production and excited spectra: Ξ**cc and Ω**cc. Ωccc might be also observed
Ø Three weakly decaying C = 2 states are expected:Ø Ξcc isodoublet (ccu; ccd) and an Ωcc isosinglet (ccs), each with JP = 1/2+
Ø Ξcc++ observed in two different decay modes!
m(⌅++cc ) = 3621.24± 0.65(stat)± 0.31(syst) MeV
<latexit sha1_base64="+sIIFXinVS1FriMNqbSgWnpfPYg=">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</latexit>
⌧(⌅++cc ) = 0.256+0.024
�0.022(stat)± 0.014(syst) ps<latexit sha1_base64="ftQaOrZmJZ7oTXaOF6/PBZQbuW0=">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</latexit>
⌅++cc ! ⌅+
c ⇡+
<latexit sha1_base64="xUsPH5ZOjRTBztCthzvj46aCw6k=">AAACEXicdVDLSsNAFJ3UV62vqEs3g0UoBErSinVZdOOygn1Ak4bJdNIOnTyYmSgl9Bfc+CtuXCji1p07/8ZJG6GKHrhwOOde7r3HixkV0jQ/tcLK6tr6RnGztLW9s7un7x90RJRwTNo4YhHveUgQRkPSllQy0os5QYHHSNebXGZ+95ZwQaPwRk5j4gRoFFKfYiSV5OoVu0fdFOPZIDWMGbQ5HY0l4jy6g5mDBwaEdkwHhquXzao5B1widfOsYTaglStlkKPl6h/2MMJJQEKJGRKib5mxdFLEJcWMzEp2IkiM8ASNSF/REAVEOOn8oxk8UcoQ+hFXFUo4V5cnUhQIMQ081RkgORa/vUz8y+sn0j93UhrGiSQhXizyEwZlBLN44JBygiWbKoIwp+pWiMeIIyxViCUVwven8H/SqVWterV2fVpuXuRxFMEROAYVYIEGaIIr0AJtgME9eATP4EV70J60V+1t0VrQ8plD8APa+xcXAZyH</latexit>
⌅++cc ! ⇤+
c K�⇡+⇡+
<latexit sha1_base64="D5jb5FOP3qo80UmKcfOtGPZ/FiM=">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</latexit>
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WHAT ABOUT Ξbc?
(e.g.)N(⌅0bc ! J/ ⇤+
c K�; Run1) =N(B+
c ! J/ D(⇤)+s ; Run1)
⇥ �(pp ! ⌅bcX)
�(pp ! B+c X)
⇥ f⌅bc!⌅0bc
⇥ Br(⌅0bc ! J/ ⇤+
c K�)
Br(B+c ! J/ D(⇤)+
s )
⇥ ✏K�
' 3 candidates
Ø The Bc meson was discovered almost two decades ago In LHCb, ~5000 Bc àJ/ψπ in Run I
So, why have we not yet seen bcq baryons (Xbc)?Lower production rates, guess σ(Xbc) ~ (0.1 -0.5) � σ(Bc+)In J/ψ modes, (usually) get a charm baryon: yield reduced by BF(Xc) � εsel(Xc) Shorter lifetime (~0.15 – 0.4 ps range, compared to ~0.5 ps for Bc)
N(⌅0bc ! J/ ⇤+
c K�; Run 5) ' 6⇥ 102
Exclusive !bb are even more unlikely but see later for an alternative approach
[arXiv:1808.08865]
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PROBING THE NATURE OF THEEXOTIC HADRONS
Ø Observation of several hadronic resonances with hidden charm or beauty(so called X, Y, Z states) in the last decade at LHC and B-factories
Ø They barely fit to standard quarkonium scenarios and “exotic”interpretations proposed: compact tetraquarks, molecules, cusps, …
Ø Most of them are quite broad and observed in 3-body decays of b-hadrons(e.g. B0 à Z(4430)- (à !(2S) "-) K+)
Upgrade II would allow to test further their nature by:Ø Probing the resonant characterØ Searching for isospin partnersØ Measurements of quantum numbers JP
Such goal relies on amplitude analysis techniques. Refinement of theoretical parametrization of hadronic amplitudes and advanced understanding of the light
spectroscopy are required in the meantime
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PROBING THE NATURE OF THEEXOTIC HADRONS
Ø What about the narrow pentaquarks Pc+ recently
observed? (See Lucio’s talk for more details)https://agenda.infn.it/event/15632/contributions/89325/
Ø Determination of quantum numbers is verylikely but observation of isospin partners isdisfavored (Pc0 àJ/! n)
]2c) [MeV/-Kp1c
c(m5450 5500 5550 5600 5650 5700
)2 cEv
ents
/ ( 5
MeV
/
020406080
100120140160180200
LHCb
-Kp1c
c®0bL-Kp
2cc®0bL
PRL 119 (2017) 062001arXiv:1902.05588
However new insights might come by:Ø Studying Pc+ in different system (e.g. B0àJ/ ! p p ) or decay modes
(e.g. "b à #c1pK)Ø Measurements of production in prompt and from b-hadron decays
3 fb-1
arXiv:1904.03947
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DOUBLY CHARMED TETRAQUARK: ccqq
Ø Doubly charmed particles are a straightforward consequence of the hiddencharmed exotic hadrons
Ø If discovered, they would be almost full-proof states made of 4 quarks
Tetraquark Loosely bound molecules
[A. Esposito et al.: PRD 88 (2013) 054029]
Between them, the doubly charged states play an important role into understanding their nature: indeed in a loosely bound molecule, Coulomb
repulsion would induce a fall-apart decay on very short time scales
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DOUBLY CHARMED TETRAQUARK: ccqq
Ø If their masses are above the DD thresholds, pure tetraquark modelspredict (narrow) states with quantum numbers JP = 0+, 1+ and 2+
Ø 0+ and 1+ states expected to be the lightest and most likely to be formed(and observed)
JP = 1+ JP = 0+
Natural widths as predicted by a pure tetraquark model
4000 4100 4200 4300 4400
1
2
5
10
20
50
M!!s!!" #MeV$
"!! s!!"#Me
V$
PV
PV!VV
PVPV!VV
Good ! state
3900 4000 4100 4200 4300 4400
1
2
5
10
20
50
M!!s!!" #MeV$
"!! s!!"#Me
V$
PP
PP!VV
PP
PP!VVBad ! state
m(D*Ds) m(D*D*s) m(DDs) m(D*D*s)
[A. Esposito et al.: PRD 88 (2013) 054029]
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DOUBLY CHARMED TETRAQUARK INPROMPT PRODUCTION
Narrow states could be easily spotted in the prompt production
Associated production of D+D+ and D+Ds+ (0.3 fb-1) [JHEP 06 (2012) 141]
N(D+D+; Run5) ' 750k candidatesN(D+D+
s ; Run5) ' 150k candidates
1.82 1.84 1.86 1.88 1.9
1.821.84
1.861.88
1.90
10
20
1.82 1.84 1.86 1.88 1.9
1.9
1.95
2
0
5
10
m(Kππ) [GeV] m(Kππ) [GeV]m(Kππ) [GeV]
m(KKπ) [GeV]
Ds+D+
D+ D+
arXiv:1808.08865
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DOUBLY CHARMED TETRAQUARKIN Bc DECAYS
Ø If the states are broad-ish à Search for them in Bc decays where the quantum numbers can be also measured
Ø The Bc meson is the lightest state in the standard model that can decay to two same-flavour charmed hadrons:
N = 28.9 � 5.6 (3 fb-1)
N(B+c ! D0D0D+
s ; Run5) ' 102 candidates
Clear signature. Expected to be background free.Three pseudoscalars in the final state
T +s (ccus) ! D0D+
s
PRD 87 ( 2013) 112012
arXiv:1808.08865
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MULTIPLETS OF PENTAQUARKS
[E. Santopinto et al.: PRD 96 (2017) 014014]
300 candidates of Ξb
- àJ/ψΛK- (3 fb-1)
LHCb: PLB 772 (2017) 265
N(⌅�b ! J/ ⇤K�; Run5) ' 6⇥ 104
As for other hadrons, multiplets of pentaquarks should exist. The observedPc+ should be states with quark content uudcc. We could look for strangepentaquark Pcs
0àJ/ψΛ in Ξb decays.
arXiv:1808.08865
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INCLUSIVE SEARCH FOR DOUBLY BEAUTYHADRONS (!bb, "bb, Xbbqq, etc…)
Yields and shape can return insights on the cross-section, mass and lifetime Theoretical inputs required to probe the composition of the bb-hadron mixture
Ø Exclusive approaches not promising (e.g. ): • Curse of BFs: 2 x (b à c) x (c à s) x efficiency
Ø What about an inclusive approach? E.g. Displaced charm hadrons used to measure inclusive #(pp→bbX)
PLB 694 (2010) 209Weakly decaying double beauty hadrons are the only
possible source of displaced Bc- mesons
Prompt charm
b à c
Bc-
T. Gershon, A. PoluektovJHEP 01 (2019) 019
Xbbud ! B�D+⇡�<latexit sha1_base64="eCdT4XsqxMKevCrN5wLgvwZ5jus=">AAACDnicdVBLSwMxGMzWV62vVY9egqUgSMu2FeuxVA8eK9gHdLdLNpttQ7MPkqxQlv4CL/4VLx4U8erZm//GdLtCFR0IGWa+j2TGiRgV0jA+tdzK6tr6Rn6zsLW9s7un7x90RRhzTDo4ZCHvO0gQRgPSkVQy0o84Qb7DSM+ZXM793h3hgobBrZxGxPLRKKAexUgqydZLfTtxHNNBHMYwvdwZNGUIW8MyvBqeQjOiw7KtF42KkQIukbpx3jAasJopRZChbesfphvi2CeBxAwJMagakbQSxCXFjMwKZixIhPAEjchA0QD5RFhJGmcGS0pxoRdydQIJU3V5I0G+EFPfUZM+kmPx25uLf3mDWHoXVkKDKJYkwIuHvJhBFXfeDXQpJ1iyqSIIc6r+CvEYcYSlarCgSvhOCv8n3VqlWq/Ubs6KzVZWRx4cgWNwAqqgAZrgGrRBB2BwDx7BM3jRHrQn7VV7W4zmtGznEPyA9v4F8HyaHw==</latexit>
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BELLE II AND LHCb AT WORK
Complementarity of the two experiments essential in exploring spectroscopyØ LHCb: larger production cross-sections, more performant for decay mode
involving charged particles (e.g. X(3872)àJ/!"", …), unique in many sectors: Bs(**), Bc(**), Ξbc(**)
Ø Belle II: smaller background, more suitable for decay modes with neutrals in the final state (e.g. X(3872)àJ/! # and its isospin/C-odd partners, …)
300 fb-150 fb-1
50 ab-1
arXiv:1808.08865
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SUMMARY
The large data set collected in the HL-LHC era, together with an upgraded detector, will boost sensitivity in searches for heavy states with
small production cross sections and/or small decay rates
Ξcc++
X(3872)
���to be continued) [MeV]-K+cX(m
3000 3100 3200 3300
Can
dida
tes /
(1 M
eV)
0
100
200
300
400 LHCb-K+cX
Full fitBackgroundFeed-downs
sidebands+cX
Ωc**
Predictions are always complicated…even more when concerning unknown states!
Pc+
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SEARCH FOR A STABLE 1++ bbud TETRAQUARK
XbbudD+
B-u
bd
b
cd
bu
du
! -
Ø Inclusive reconstructive efficiencies for B mesons are low at LHCb due to low branching fractions into low multiplicity final states
Ø Not promising even for Upgrade II!
Ø It would have observable lifetime, this combinatorial background would be under control
Ø Unfortunately bbq baryons have not been observed yet, reflecting low prompt production rates expected for both b quarks to end up in the same hadron, and difficulty in reconstruction of two subsequent weak decays of b quark
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IMPACT OF CALORIMETER UPGRADE
]2c) [MeV/-Kp1c
c(m5450 5500 5550 5600 5650 5700
)2 cEv
ents
/ ( 5
MeV
/
020406080
100120140160180200
LHCb
-Kp1c
c®0bL-Kp
2cc®0bL
Ø Measurement of B(X(3872)àψ(2S) γ)/B(X(3872)àJ/ψ γ) [Nucl.Phys.B886 (2014) 665]
Ø Search for pentaquarks decaying to χc1p where χc1àJ/ψ γ[LHCb: PRL 119 (2017) 062001]
BR(X(3872) ! (2S)�)
BR(X(3872) ! J/ �)= 2.46± 0.64± 0.29 Pure molecule scenario
disfavored
Ø Increased calorimeter resolutionØ Reduction in background by a fast timing
calorimeter informationØ Increased sensitivity to low pT photon and π0
See Preema Pais’s Talk on Wednesday
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IMPACT OF CALORIMETER UPGRADE
X(3872) (JPC = 1++) X(3872) (JPC = 1+-)C-odd partner
(tetraquark/molecule)
~
J/ψ ηIsospin partner
(tetraquark/molecule)
X(3872)�
J/ψ π±π0
Xb
ϒ(1S)ωπ+π-π0
Neutrals will be crucial into probing further the X(3872) meson
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IMPACT OF VELO UPGRADE
Removal of RF foilØ Improved vertex resolutionØ Higher signal efficiency with large
background rejectionØ Increased track efficiencyØ Reduction in ghost rates
Ø Better performance into detecting low momentum tracks will contributeinto studying/observing excited states decaying through dipion transitions(e.g. Bc* à Bc π π)
Ø Better reconstruction efficiency for multibody B decays, such as BàDDKaiming to the search for charmonium-like states
Ø Improved vertex resolution è Higher efficiency into selecting short-livedparticles: Bc, Ξcc, Ωcc, Ξbc, Ωccc
LHCb Simulation
LHCb Simulation