LHC$results$on$open$charm,$double$ charm$and$X(3872 ... · LHC$results$on$open$charm,$double$...
Transcript of LHC$results$on$open$charm,$double$ charm$and$X(3872 ... · LHC$results$on$open$charm,$double$...
LHC results on open charm, double charm and X(3872) produc<on
Patrick Robbe, LAL Orsay, 14 May 2012 For the LHCb Collabora<on
Charm 2012 Honolulu 14 – 17 May 2012
• Results from the LHC obtained with pp collisions at 7 TeV in 2010 and 2011.
• Prompt open charm produc<on: – Cross-‐sec<ons, – Excited states spectroscopy.
• Mul<ple charm produc<on: D+D, D+J/ψ and J/ψ+J/ψ
• X(3872) produc<on.
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Outline
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The LHC experiments
LHCb ALICE
High luminosity and pile-‐up
Low or moderate luminosity and pile-‐up
ATLAS CMS
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The LHC experiments • All experiments have a heavy
flavour physics program. • They explore complementary region
of phase space. • Most results presented here from
LHCb (experiment dedicated to b and c physics)
• Based on early data recorded with minimum bias triggers, – In the central region: |y|<0.5, 5 nb-‐1 ALICE, JHEP01(2012) 128. – In the forward region: 2<y<4.5, 2 nb-‐1 LHCb, LHCb-‐CONF-‐2010-‐013.
• Feed-‐down from B decays es<mated (and subtracted) using impact parameter distribu<ons: prompt D point back to the primary vertex.
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Prompt charm cross-‐sec<ons
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Prompt charm cross-‐sec<ons (central region)
D0➝K-‐π+ + c.c. D+➝K-‐π+π+ + c.c. D*+➝D0π+ + c.c.
• Measurements compared and in good agreement with pQCD based theore<cal models: – FONLL, M. Cacciari et al. [CERN-‐PH-‐TH-‐2011-‐227] – GM-‐VFNS, B. Kniehl et al.
GeV/c t
p0 5 10 15 20 25
b/G
eV/c
)µ
(
|y|<
0.5
| t /
dpmd
-210
-110
1
10
210
310ALICE
-1 = 5 nbint = 7 TeV, Ls, pp 0D
1.3% BR norm. unc. (not shown)± 3.5% lumi, ±
stat. unc.syst. unc.
FONLL GM-VFNS
(GeV/c)tp0 5 10 15 20 25
FON
LLD
ata
00.5
11.5
22.5
33.5
(GeV/c) t
p0 5 10 15 20 25
GM
-VFN
SD
ata
00.5
11.5
22.5
33.5
GeV/c t
p0 5 10 15 20 25
b/G
eV/c
)µ
(
|y|<
0.5
| t /
dpmd
-210
-110
1
10
210
310ALICE
-1 = 5 nbint = 7 TeV, Ls, pp +D
2.1% BR norm. unc. (not shown)± 3.5% lumi, ±
stat. unc.syst. unc.
FONLL GM-VFNS
(GeV/c)tp0 5 10 15 20 25
FON
LLD
ata
00.5
11.5
22.5
33.5
(GeV/c) t
p0 5 10 15 20 25
GM
-VFN
SD
ata
00.5
11.5
22.5
33.5
GeV/c t
p0 5 10 15 20 25
b/G
eV/c
)µ
(
|y|<
0.5
| t /
dpmd
-210
-110
1
10
210
310ALICE
-1 = 5 nbint = 7 TeV, Ls, pp *+D
1.5% BR norm. unc. (not shown)± 3.5% lumi, ±
stat. unc.syst. unc.
FONLL GM-VFNS
(GeV/c)tp0 5 10 15 20 25
FON
LLD
ata
00.5
11.5
22.5
33.5
(GeV/c) t
p0 5 10 15 20 25
GM
-VFN
SD
ata
00.5
11.5
22.5
33.5
ALICE, JHEP01(2012) 128
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Prompt charm cross-‐sec<ons (forward region)
• Double differen<al cross-‐sec<ons (pT and y) compared with the same models. • Comparison with PYTHIA generator (configured with « LHCb tunings »)
D0➝K-‐π+ + c.c. D+➝K-‐π+π+ + c.c.
LHCb, LHCb-‐CONF-‐2010-‐013
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Prompt charm cross-‐sec<ons (forward region)
Ds+➝K-‐K+π+ + c.c.
D*+➝D0π+ + c.c.
• The total cc cross-‐sec<on is σ(pp➝cc+X) = 6100 ± 934 µb – Combining the D0, D+, D*+ and Ds
+ cross-‐sec<ons, – Using the hadroniza<on frac<ons (c ➝ D0/D+/Ds/D*+) measured at the Z0 and Y(4S) – Extrapola<ng from the LHCb acceptance to 4π using PYTHIA
• To be compared with the total inelas<c cross-‐sec<on, ~60 mb.
• ALICE also measured the cross-‐sec<ons at the intermediate energy of 2.76 TeV
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Prompt charm cross-‐sec<ons at various energies
GeV/c t
p0 2 4 6 8 10 12 14
b/G
eV
/cµ
|y|<
0.5
| t / d
p!
d
-210
-110
1
10
210
+" +" -
K# +D-1 = 2.76 TeV, 1.1 nbspp,
= 54 mbMB
!
7% global norm. unc. (not shown)±
ALICE Preliminary
stat. unc.
syst. unc.
FONLL
GM-VFNS
GeV/c t
p0 2 4 6 8 10 12 14
b/G
eV
/cµ
|y|<
0.5
| t / d
p!
d
-210
-110
1
10
210
+" -
K# 0D-1 = 2.76 TeV, 1.1 nbspp,
= 54 mbMB
!
7% global norm. unc. (not shown)±
ALICE Preliminary
stat. unc.
syst. unc.
FONLL
GM-VFNS
Total cc cross-‐sec<on (in 4π) for different energies, different experiments, and compared to pQCD models (Mangano, Nason, Ridolfi, [Nucl. Phys. B 373 (1992) 295]).
( GeV/c )t
p0 2 4 6 8 10 12 14
b/G
eV
/c )
µ (
|y
|<0
.5 | t
/ d
p!
d
-210
-110
1
10
210
-1 = 2.76 TeV, 1.1 nbs, pp *+D
= 54 mbMB!
7% global norm. unc. (not shown)±
ALICE Preliminary
stat. unc.
syst. unc.
FONLL
GM-VFNS
• Large frac<on of the produced charm mesons comes from the decay of (orbitally) excited states.
• LHCb data allows to study the D(s)J states, in par<cular the ones recently observed at B factories, some of them needing confirma<on.
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Excited charm state produc<on
DJ➝D(*)π DsJ➝D(*)K
• With 320 pb-‐1 of LHCb data (beginning of 2011) • Exclusive reconstruc<on with the modes
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Excited charm state reconstruc<on
DJ
DsJ
D*+π-‐
D+π-‐
D0π+
D*+KS0 D+KS0 D0K+
D+➝K-‐π+π+ D*+➝D0π+
D0➝K-‐π+ KS0➝π+π-‐
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D0π+, D+π-‐ and D*+π-‐ Spectra
D0π+
D*+π-‐
D+π-‐
D2*(2460)0 D2
*(2460)+
D1*(2420)0 D2
*(2460)0
Feed-‐down from D1
*(2420)0, D2
*(2460)0 Feed-‐down from D1
*(2420)+, D2
*(2460)+
• Regions of the new states reported by BABAR [Phys. Rev. D82,111101(2010)]: – D(2550)0, D*(2600)0,
D*(2750)0, D*(2760)0
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D0K+, D+Ks0 and D*+Ks0 Spectra
D*+Ks0
D+Ks0
D0K+
Ds2*(2573)+ Ds1
*(2536)+
Ds2*(2573)+
Feed-‐down from Ds1
*(2536)+ Feed-‐down from Ds1
*(2536)+
• Regions of the new states reported by BaBar [Phys. Rev. D80,092003(2009)]: – Ds1
*(2710)+, Dsj*(2860)+ ,
Dsj*(3040)+
• Possible sources of double charm in hadron collisions (apart from cc produc<on): – High order charm produc<on from gluons:
• gg➝J/ψ J/ψ, gg➝ J/ψcc, gg➝cccc. • Could enhance prompt J/ψ produc<on (sensi<vity to Color Octet LDME)
• Computed at NNLO* (eg J.-‐P. Lansberg. [Eur.Phys.J. C61 693 (2009)])
– Intrinsic charm content of the proton. – Double parton scauering: 2 hard processes in a single pp collision.
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Double charm produc<on
• J/ψ pairs observed first in pN interac<ons by NA3 (150 and 280 GeV) [Phys. Leu. B 114, 457 (1982), Phys. Leu. B 158, 85 (1985)]
• At LHCb, measurement of the J/ψ J/ψ produc<on cross-‐sec<on at 7 TeV, in the forward region: 2<y<4.5 and pT<10 GeV/c for both J/ψ: – 37.5 pb-‐1 [Phys. Leu. B 707 (2012) 52]
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Double charmonium produc<on
NA3 NA3
• Standard simple selec<on of single J/ψ candidates in the µ+µ-‐ decay mode.
• Background from 2 J/ψ produced in different pile-‐up collisions or in the decay of a B hadron removed requiring the 2 J/ψ come from a common vertex.
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Double charmonium produc<on
• Raw signal distribu<on: number of first J/ψ candidates (from a mass fit) in bins of the invariant mass of the second candidate.
• Fit with a double Crystal Ball func<on for the signal and an exponen<al for the background gives NJ/ψJ/ψ = 141 ± 19.
• Absolute cross-‐sec<on is obtained from the knowledge of the total efficiency (reconstruc<on, selec<on, trigger)
• Each event is corrected for its efficiency and the number of signal events axer correc<on is obtained from a fit to the corrected mass distribu<on: – NJ/ψJ/ψ = 672 ± 129
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Double J/ψ cross-‐sec<on
• Integrated cross-‐sec<on:
• Ra<o to prompt (single) J/ψ cross-‐sec<on:
• Theore<cal expecta<ons in LHCb acceptance: – LO CSM with Single Parton Scauering (including feeddown from ψ(2S)): 4.1 ± 1.2 nb. [A. V. Berezhnoy et al., Phys. Rev. D84 (2011) 094023]
– Contribu<on from Double Parton Scauering: 2 ± 1 nb. [A. Novoselov, arXiv:1106.2184]
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Double J/ψ cross-‐sec<on results
σ J /ψJ /ψ =NJ /ψJ /ψ
corr
LB2 (J /ψ→ µ+µ− )= 5.1±1.0±1.1nb
σ J /ψJ /ψ
σ J /ψ
= 5.1±1.0± 0.6−1.0+1.2( )×10−4
Phys. Leu. B 707 (2012) 52
• Cross-‐sec<on as a func<on of M(J/ψ J/ψ)
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Double J/ψ invariant mass
• Yellow area: theore<cal expecta<ons from LO CSM [A. V. Berezhnoy et al., Phys. Rev. D84 (2011) 094023]
• More sta<s<cs needed to study possibility of charm tetraquarks (low mass) or decays of χb➝J/ψ J/ψ (~9 GeV/c2)
• C = D0 (➝K-‐π+), D+(➝K-‐π+π+), Ds+(➝φπ+) and Λc
+(➝pKπ) • With 355 pb-‐1 of LHCb data (~30% of the 2011 data
sample), study, – J/ψ C (or J/ψ C) – C C (or C C) – C C: dominated by « normal » gg➝cc, but interes<ng probe of the underlying produc<on mechanisms through correla<ons, ….
• In the range: • 2 < yC,J/ψ < 4, • 3 < pT,C < 12 GeV/c, • pT,J/ψ < 12 GeV/c.
– [arXiv:1205.0975, LHCb-‐PAPER-‐2012-‐003] 20
Double charm produc<on – open charm
cc cc
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Single hadron selec<on
• Large and clean signal samples:
J/ψ
D0
Ds+
D+
Λc+
• Combine hadron, with vertex requirement to remove contamina<on from pile-‐up and B hadron decays.
• Charge conjugate modes included in the plots
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Double charm signals – J/ψ + C
• Number of signal candidates from a bidimensional mass fit
J/ψ D0 J/ψ D+
J/ψ Ds+
J/ψ Λc+
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Double charm signals – C + C D0 D0 D0 D+
D0 Ds+ D0 Λc
+
D0 D0 D0 D+
D0 Ds+ D0 Λc
+
• Per-‐event efficiency correc<ons (es<mated from data directly when possible) applied to compute absolute produc<on cross-‐sec<ons.
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Double charm cross-‐sec<ons
Compared with gg ➝J/ψ c c computa<ons: A. V. Berezhnoy et al., Phys. Rev. D57 (1998) 4385 J.-‐P. Lansberg, Eur. Phys. J C61 (2009) 693
LHCb-‐PAPER-‐2012-‐003
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Double charm proper<es
• Angular correla<ons in J/ψ C and C C events: no evidence for correla<ons
• For C C, enhancement at small Δφ, consistent with cc produc<on via the gluon spli{ng process.
• At hadron colliders two sources: – Prompt produc<on, domina<ng, – Feed-‐down from B decays, with lower rate, but with interes<ng proper<es.
• First data used to measure – Inclusive produc<on:
• LHCb, 34.7 pb-‐1, arXiv:1112.5310, LHCb-‐PAPER-‐2011-‐034 • CMS, 40 pb-‐1, CMS PAS BPH-‐10-‐018
– Mass: • LHCb, 34.7 pb-‐1, arXiv:1112.5310, LHCb-‐PAPER-‐2011-‐034
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X(3872) produc<on
• Reconstructed in the decay mode X(3872) ➝J/ψπ+π-‐, J/ψ➝µ+µ-‐
• In two complementary regions: – CMS: pT > 8 GeV/c and |y| < 2.2 – LHCb: 5 < pT < 20 GeV/c and 2.5 < y < 4.5.
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X(3872) produc<on
565 ± 62 signal candidates
σ x BR ~ 5.1 nb
Using CMS ψ(2S) cross-‐sec<on [JHEP02 (2012) 011]
• Important quan<ty to understand the nature of this par<cle (conven<onal charmonium, molecule, tetraquark): comparison with DD* threshold.
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X(3872) mass
• Systema<c uncertain<es dominated by knowledge of the momentum scale and of the energy loss in the detector material.
• To compare with – M(D0)+M(D*+)=3871.79±0.29 MeV/c2.
]2X(3872) mass [MeV/c3867 3868 3869 3870 3871 3872 3873 3874
CDF
+BaBar B0BaBar B
D0
Belle (arXiv:1107.0163)
LHCb (arXiv:1112.5310)
0.18±New average 3871.66
)*)+M(D0M(D
]2X(3872) mass [MeV/c3867 3868 3869 3870 3871 3872 3873 3874
LHCb-‐PAPER-‐2011-‐034
• Early data of the LHC allowed to measure produc<on cross-‐sec<ons of: – Open charm: large cross-‐sec<ons – X(3872)
• Large data samples to study in details produc<on proper<es: – Excited states, – Angular correla<ons.
• Observa<on (first observa<ons for some of them) of double charm produc<on, with large cross-‐sec<ons: interes<ng window to study and understand charm and charmonium produc<on mechanisms.
• Only part of the samples analyzed, other analyses will appear soon. • LHC is delivering 8 TeV collisions this year: produc<on measurements to
be repeated at this higher energy.
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Conclusions