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LHCb as a fixed-target experimentStatus and short-term prospects
6.5 TeV proton
He atrest
antiproton
Giacomo Graziani (INFN Firenze)on behalf of the LHCb Collaboration
Physics Beyond Colliders Annual WorkshopNovember 21, 2017
The LHCb DetectorLHCb is the LHC experiment with “fixed-target like” geometryvery well suited for. . . fixed target physics!
JINST 3, (2008) S08005
fully instrumented in the pseudorapidity range 2 < η < 5
excellent vertexing, tracking, PIDflexible trigger with high bandwidth: hardware level up to 1 MHz, software level withoffline-quality event reconstruction
G. Graziani slide 2 PBC, Nov 21 2017
SMOG: the LHCb internal gas target
The System for Measuring Overlap with Gas(SMOG) allows to inject small amount of no-ble gas (He, Ne, Ar, . . . ) inside the LHCbeam around (∼ ±20 m) the LHCb collisionregionExpected pressure ∼ 2× 10−7 mbar
Originally conceived for the luminosity determinationwith beam gas imaging JINST 9, (2014) P12005Became the LHCb internal gas target for a rich and var-ied fixed target physics program
G. Graziani slide 3 PBC, Nov 21 2017
SMOG samples on tape2012 First pilot runs with p and Pb beams on Neon2015 Several data samples with He, Ne and Ar targets acquired during special runs (e.g. VdM
scans) with limited beam intensity and without interference with pp data taking2016 Other special runs with helium gas2017 First high-intensity SMOG run currently ongoing, with proton beam of nominal intensity
on Neon. Acquiring simultaneously beam-gas collision (when beam1 bunches cross thedetector without colliding) and beam-beam collisions for standard LHCb physics (up to 742non colliding and 1094 colliding bunches)
pNe pHe pAr pAr PbAr pHe pHe pNe pNe
]22
prot
ons
(Pb)
on
targ
et [
10
2−10
1−10
1
10
210
2500 GeV
4000 GeV
6500 GeV
Beam Energy
2015 | 2016 | 2017
L ∼ 5 nb−1 × pot
1022× pgas
2× 10−7 mbar× Exp_Efficiency
G. Graziani slide 4 PBC, Nov 21 2017
The pros of fixed target
Study different collisions systems at differentenergy scales within the same experimentAccess to large-x region also at moderate Q2
G. Graziani slide 5 PBC, Nov 21 2017
Physics Menu
Unique measurements already achievable with few/nb:Study charm production at
√sNN ∼ 100 GeV on different nuclei
è Cold Nuclear Matter effects, sensitivity to (n)PDFs at large xproduction measurements in soft QCD realm at
√sNN ∼ 100 GeV
large model uncertainties, great interest for Cosmic Rays physics
The first two preliminary results from SMOG released during 2017
Future:several ideas for improved targets understudy, which could greatly widenthe physics program:larger densitywider range of nucleipossible target polarizationcrystal targets
See talks byP. Di Nezza (LHCSpin)J.-P. Lansberg (AFTER)A. Stocchi (Crystal exps)M. Ferro Luzzi (LHC FT)
G. Graziani slide 6 PBC, Nov 21 2017
First charm in LHC fixed targetLHCb-CONF-2017-001
Obtained from the first small (few nb−1) p-Ar data sample acquired in 2015First demonstration analysis, but differential shapes (y, pT, xF ) expected toconstrain modelsmore theoretical predictions needed!
G. Graziani slide 7 PBC, Nov 21 2017
Acessing high-x region LHCb-CONF-2017-001Distributions of x2 ≡ (Me−y∗)/
√sNN
Possibility to constrain Intrinsic charm and antishadowing in nPDFs.G. Graziani slide 8 PBC, Nov 21 2017
Inputs to Cosmic Ray Physics I
Intrinsic charm important for high-energy neutrino astrophysics:background for the ICECUBE experiment is dominated by open charmproduction in atmospheric showerspredictions are based on measurements at xF ∼ 0 (like pp collisions in LHCb)possible relatively large contribution from intrinsic charm
IceCube, arXiv:1705.07780
4
Ei2
[GeV
cm
-2 s-1
sr-1
]
Eie [GeV]
10-10
10-9
10-8
10-7
10-6
103 104 105 106
dotted grey: Conv. Atm. ie
Intrinsic Charm
solid grey: Conv. Atm. ie + BERSS
solid black: Conv. Atm. ie + Intrinsic Charm (H3A) + BERSS
IceCube astrophysical flux
IceCube atmospheric ie
Ei2
[GeV
cm
-2 s-1
sr-1
]
Eiµ [GeV]
10-10
10-9
10-8
10-7
10-6
103 104 105 106
Intrinsic Charm
dotted grey: Conv. Atm. iµ solid grey: Conv. Atm. iµ + BERSS
solid black: Conv. Atm. iµ + Intrinsic Charm (H3A)
+ BERSS
IceCube astrophysical flux
IceCube iµ
FIG. 2. Left: Comparison of the total atmospheric νe + ν̄e data (IceCube-86 for 332 days) with calculations. The contributionto the νe + ν̄e flux from intrinsic charm for Case (A) for various cosmic ray spectra is shown by the dashed lines (H3A =magenta, H3P = green, H14A = brown, and H14B = magenta. H14A and H14B are on top of each other). The conventionalνe + ν̄e flux [123], conventional νe + ν̄e + BERSS (H3A), and conventional νe + ν̄e + BERSS + intrinsic charm contributionfor H3A are shown. Right: Same as the left panel, but for νµ + ν̄µ [6] (IceCube-79/ 86 for 2 years). This measurement alsoincludes the astrophysical neutrino flux. The astrophysical flux shown in these panels is from Refs. [4].
contribution follows the inelastic cross section [127].
We solve Eqs. 1 – 3 separately in the low and highenergy regime [57, 58, 64, 70, 72]. The final prompt neu-trino flux is a geometric interpolation of the low and highenergy solutions and includes the contribution of all thecharm hadrons, D0, D̄0, D±, D±s ,Λ
+c .
Our calculation improves over the previous esti-mates [56, 57, 78–80] in various important ways. Wenormalize our calculations to the ISR and the LEBC-MPS collaboration data [86, 87], which were not usedin the earliest works. We employ the latest cosmic rayflux measurement, and the experimentally measured nu-clear scaling of the cross section, and a theoreticallymotivated energy dependence of the cross section. Weuse a more updated calculation of the intrinsic charmcross section which takes into account the inherent non-perturbativeness of the process [124, 125] whereas someof these earlier works [78, 79] used a modified pQCD pre-scription to account for the high xF data.
Results: Our predictions for the flux of neutrinos (νµ+ν̄µ or νe + ν̄e) are shown in Fig. 1. The highest, interme-diate and the lowest flux are given by Case (A), Case (B),and Case (C) respectively. We also show the flux calcu-lated by BERSS [69], GMS [72], GRRST [70], HW1 [78],HW2 [79], and ERS w/G [6, 85]. Due to the uncertaintiesin parametrizing the g → cc̄ contribution, the resultingneutrino flux has an uncertainty of a factor of ∼ 5 [70].
Remarkably, we find that the atmospheric prompt neu-trino flux due to intrinsic charm is at the same level asthe pQCD contribution.
The neutrino fluxes due to intrinsic charm are largeenough to be detectable by IceCube. If IceCube does notdetect atmospheric prompt neutrinos at these flux lev-els, then it will imply strong constraints on the intrinsiccharm content of the proton.
In the intrinsic charm picture, the proton preferen-tially forms a charm hadron with a similar energy. Inthe g → cc̄ picture, due to its steeply falling dσ/dx dis-tribution, the charm hadron comes dominantly from aproton at much higher energy. A rapid energy depen-dence, disfavored by Refs. [124, 125], is used in Ref. [78],and this results in a much higher neutrino flux. Our re-sults are slightly lower than the calculation presented inRef. [79] due to the above mentioned refinements.
So far, IceCube has presented upper bounds on promptneutrinos. IceCube assumes that the prompt neutrinoflux is the ERS w/G spectrum and varies the normal-ization. IceCube takes into account the muon veto fordowngoing events via a likelihood analysis. The presentlimit on the prompt neutrino spectrum is 1.06 times theERS w/G flux [7]. These IceCube limits are close to theintrinsic charm prompt neutrino spectrum predictions,implying that IceCube can give information about in-trinsic charm content of the proton in the near future.
In Fig. 2 (left), we compare our calculation for Case (A)and the measurement of the atmospheric νe flux [123].
Laha and Brodsky, arXiv:1607.08240G. Graziani slide 9 PBC, Nov 21 2017
Inputs to Cosmic Ray Physics II
AMS02 results provide unprecedented accuracy for measurement of p/p ratio in cosmic raysat high energies PRL 117, 091103 (2016)
hint for a possible excess, and milder en-ergy dependence than expectedprediction for p/p ratio from spallationof primary cosmic rays on intestellarmedium (H and He) is presently limitedby uncertainties on p production cross-sections, particularly for p-Heno previous measurement of p productionin p-He, current predictions vary within afactor 2the LHC energy scale and LHCb +SMOGare very well suited to perform this mea-surement
�posed to the olderdata. The curve labelled ‘fiducial’ assumes
the reference values for the different contributions to the uncertainties: best fit proton and heliumfluxes, central values for the cross sections,propagation and central value for the Fisk potential.
We stress however that the whole uncertainty band can be spanned within the errors.
than primary, �p/p flux. Notice that the shaded yellow area does not coincide with the Min-Med-Max envelope (see in particular between 50 and 100 GeV): this is not surprising, as itjust reflects the fact that the choices of the parameters which minimize and maximize the p̄/psecondaries are slightly different from those of the primaries. However, the discrepancy is notvery large. We also notice for completeness that an additional source of uncertainty affects theenergy loss processes. Among these, the most relevant ones are the energy distribution in theoutcome of inelastic but non-annihilating interactions or elastic scatterings to the extent theydo not fully peak in the forward direction, as commonly assumed [55]. Although no detailedassessment of these uncertainties exists in the literature, they should affect only the sub-GeVenergy range, where however experimental errors are significantly larger, and which lies outsidethe main domain of interest of this article.
Finally, p̄’s have to penetrate into the heliosphere, where they are subject to the phenomenonof Solar modulation (abbreviated with ‘SMod’ when needed in the following figures“). We de-scribe this process in the usual force field approximation [52], parameterized by the Fisk po-tential φF , expressed in GV. As already mentioned in the introduction, the value taken by φFis uncertain, as it depends on several complex parameters of the Solar activity and thereforeultimately on the epoch of observation. In order to be conservative, we let φF vary in a wideinterval roughly centered around the value of the fixed Fisk potential for protons φpF (analo-gously to what done in [25], approach ‘B’). Namely, φF = [0.3, 1.0] GV ' φpF ± 50%φpF . Infig. 1, bottom right panel, we show the computation of the ratio with the uncertainties related
6
Giesen et al., JCAP 1509, 023 (2015)
G. Graziani slide 10 PBC, Nov 21 2017
Antiprotons in p-He LHCb-CONF-2017-002
Data collected in May 2016, with proton en-ergy 6.5 TeV,
√sNN = 110 GeV
Most data from a single LHC fill (5 hours)Minimum bias trigger, fully efficient on can-didate eventsExploit excellent particle identification(PID) capabilities in LHCb to count antipro-tons in (p, pT) bins within the kinematic range
12 < p < 110 GeV/c, pT > 0.4 GeV/c
Data p 21.4 - 24.4 pt 1.2- 1.5
DLL (p -K)-200 -100 0 100 200
)πD
LL
(p
-
-200
-150
-100
-50
0
50
100
150
200
LHCb Preliminary
-200 -100 0 100 200-200
-150
-100
-50
0
50
100
150
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0
20
40
60
80
100
120
140Template for p
-200 -100 0 100 200-200
-150
-100
-50
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50
100
150
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0
100
200
300
400
500600
700
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900πTemplate for
-200 -100 0 100 200-200
-150
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-200 -100 0 100 200-200
-150
-100
-50
0
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0
10
20
30
40
50
60Template for ghost
pK−
π−
Normalization from p-e− elastic scattering Exploit excellent vertexing capa-bilities to separate prompt anddetached components. Only theprompt component included inthis preliminary result (analysis ofcomponent from hyperon decayswill follow).Background from gas contamina-tion measured to be 0.6± 0.2%
G. Graziani slide 11 PBC, Nov 21 2017
Result for cross section, ratio with modelsLHCb-CONF-2017-002
DA
TA/P
RE
DIC
TIO
N
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 12.0 < p < 14.0 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
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1
1.5
2
2.5
3 14.0 < p < 16.2 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
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1
1.5
2
2.5
3 16.2 < p < 18.7 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 18.7 < p < 21.4 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 21.4 < p < 24.4 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 24.4 < p < 27.7 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 27.7 < p < 31.4 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 31.4 < p < 35.5 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 35.5 < p < 40.0 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 40.0 < p < 45.0 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 45.0 < p < 50.5 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 50.5 < p < 56.7 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 56.7 < p < 63.5 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 63.5 < p < 71.0 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.5
1
1.5
2
2.5
3 71.0 < p < 79.3 GeV/cLHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.51
1.52
2.53 79.3 < p < 88.5 GeV/c
LHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.51
1.52
2.53 88.5 < p < 98.7 GeV/c
LHCb Preliminary
[GeV/c]T
p0 1 2 3 4
data
/ pre
dict
ion
0.51
1.52
2.53 98.7 < p < 110.0 GeV/c
LHCb Preliminary
Trasverse Momentum (GeV/c)
EPOS LHC
EPOS 1.99
QGSJETII-04
HIJING 1.38
Total uncertainty ∼ 10% for mostbins. Models can differ by more than
a factor 2.
Cross section is larger by factor∼ 1.5 wrt EPOS LHC (mostly from
larger p rate per collision).Better agreement with
EPOS 1.99, HIJING 1.38 andQGSJET-IIm (low energy extension
of QGSJET-II-04, not shown)
G. Graziani slide 12 PBC, Nov 21 2017
Inputs to Cosmic Ray Physics IIIMuon puzzle in the understanding of UHECR atmosphericshowers: yield and lateral profile of muons are used asproxy of impinging particle mass, but are not well predictedby current models
muon yield at given energy is critically dependent onproduction of nucleons and kaonslarge uncertainties from nuclear effects since data withnitrogen and oxygen targets are sparse
proton-Neon SMOG data provide a good model forinteraction in air, energy corresponds to 3rd to 4th in-teraction for a 1010 GeV shower. Measurement at mid-rapidity useful to model lateral shower developmentUse of nitrogen target not excluded in the future
G. Graziani slide 13 PBC, Nov 21 2017
Prospects for soft QCD
production of charged hadrons (p/p, π±, K±) is also being measured for thethree different targets (He, Ne, Ar). Ratios of particle species, not affected byuncertainty on luminosity, can provide precise constraints to soft QCD models
We plan to extend the study of p pro-duction to hyperon decays (account-ing for 20-30% of the production).LHCb can cleanly select decays of Λ
] 2 c Invariant Mass [MeV/+πp1100 1110 1120 1130
2 cC
and
idat
es /
0.6
MeV
/
100
200
300
] 2 c Invariant Mass [MeV/+πp1100 1110 1120 1130
2 cC
and
idat
es /
0.6
MeV
/
100
200
300
2c 0.03 MeV/± = 1115.75 µ 2c 0.33 MeV/± = 1.23 σ
36±N = 1177
LHCb = 0.9 TeVs
Λ→pπ+
0.25 < pT < 2.50 GeV/c
2.5 < y < 3.0
JHEP 1108 (2011) 034
Another p-He run was performed in november 2016 with a 4 TeV beam(√sNN =87 GeV) è scaling violation can be constrained
investigating our potential for antinuclei d, t and 3He
G. Graziani slide 14 PBC, Nov 21 2017
Prospects for heavy flavoursA rich charm harvest expected from data on tape: comparison of different targets, study otherstates (Λ+
c baryons, D+s , . . . )
]2c) [MeV/-µ +µm(2950 3000 3050 3100 3150 3200
)2 cC
andi
date
s / (
10 M
eV/
0
20
40
60
80
100 = 87 GeV pHeNNs
LHCb preliminaryJ/psi
→ µ+µ−
pHe
]2c) [MeV/-π +π -m(K1800 1820 1840 1860 1880 1900 1920 1940
)2 cC
andi
date
s / (
4 M
eV/
0
50
100
150
200
250
300
= 110 GeV pArs
LHCb preliminary
-π +π - K→ +D
D+
→ K−π+π−
pAr
]2c) [MeV/+π -m(K1800 1820 1840 1860 1880 1900 1920 1940
)2 cC
andi
date
s / (
5 M
eV/
0
100
200
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500
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700
= 87 GeV pHeNNs LHCb preliminaryD0
→ K−π+
pHe
]2c) [MeV/+π + K-
m( K1900 1920 1940 1960 1980 2000 2020 2040
)2 cC
andi
date
s / (
6.4
MeV
/
0
20
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60
80
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120
= 110 GeV pArs
LHCb preliminary
+π + K- K→ s+D
D+s
→ K−K+π−
pAr
]2c) [MeV/+π -m(p K2220 2240 2260 2280 2300 2320 2340 2360
)2 cC
andi
date
s / (
6.4
MeV
/
0
10
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= 110 GeV pArs
LHCb preliminary
+π - p K→ +cΛ
Λ+c
→ pK−π+
pAr
]2c) [MeV/+π 0m(D1940 1960 1980 2000 2020 2040 2060 2080
)2 cC
andi
date
s / (
2.67
MeV
/
0
50
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= 110 GeV pArs
LHCb preliminary
+π 0 D→ *+D
D∗+
→ D0π+
pAr
Large gain in statistics (factor 10-100) expected from currently ongoing high-intensity run ,despite larger backgrounds from ghost collisions and beam-induced residual gasè higher accuracy, extend study to ψ(2S), . . .
G. Graziani slide 15 PBC, Nov 21 2017
Conclusions
Big progress with LHCb fixed target program during the last yearFirst results demonstrate physics potentialCharm production in fixed target data expected to provide crucial inputs tounderstand CNM effects and Intrinsic CharmLHCb became an unexpected contributor to cosmic ray physics!
Improving the hardware: new calibrated pressure gauge installed during lastwinter shutdown è cross-check of the luminosity determination
Setting the ground for future fixed target programs at LHCbevaluating several proposals for new targets è talks in this workshop
G. Graziani slide 16 PBC, Nov 21 2017
Additional Material
G. Graziani slide 17 PBC, Nov 21 2017
the VErtex LOcatorCrucial detector for all SMOG studiesoptimized for forward tracks, allowing impact parameter resolution of 15 + 29/pT (GeV ) µm
JINST 9 (2014) P09007
G. Graziani slide 18 PBC, Nov 21 2017
Acceptance for SMOG eventsJINST 3, (2008) S08005
Int.J.Mod.Phys.A30 (2015) 1530022
p [GeV/c]20 40 60 80 100
[G
eV/c
]Tp
0
0.5
1
1.5
2
2.5
3
3.5
4
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
=5η
=4.5η
LHCb Preliminary
LHCb-CONF-2017-002
Total acceptance × reconstructionefficiency for antiprotons
Tracking efficiency estimated fromsimulation, validated on (pp) data
G. Graziani slide 19 PBC, Nov 21 2017
RICH PerformanceEur. Phys. J. C 73 (2013) 2431
Particle separation in RICH1 K/p separation vs momentum
G. Graziani slide 20 PBC, Nov 21 2017
Background from Residual Vacuum
Residual vacuum in LHC is not so small (∼ 10−9 mbar ) compared to SMOG pressureCan be a concern, especially for heavy contaminants (larger cross section than He), andbeam-induced local outgassingDirect measurement in data: about 15% of delivered protons on target acquired before Heinjection (but with identical vacuum pumping configuraton)
PV Track Multiplicity5 10 15 20 25 30 35 40
frac
tion
of c
andi
date
s
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
p on He gas
p on Residual Vacuum
LHCb Preliminary
LHCb-CONF-2017-002
Gas impurity found to be small:0.6± 0.2%PV multiplicity in residual vacuumevents is lower than in He events, buthas longer tails è confirm findingsfrom Rest Gas Analysis that resid-ual vacuum is mostly H2, with smallheavy contaminants
G. Graziani slide 21 PBC, Nov 21 2017
Results for D0 and J/ψLHCb-CONF-2017-001
pT and y∗
spectra for J/ψ
]c [MeV/T
pTransverse momentum 0 1 2 3 4 5 6 7 8
310×
Tp
/dψ
J/dN
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
= 110 GeV pArNNs LHCb preliminary
Rapidity in centre-of-mass y*3− 2.5− 2− 1.5− 1− 0.5− 0
/dy*
ψJ/
dN
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2310×
= 110 GeV pArNNs LHCb preliminary
compared to Pythia8 predictions and phenom. parameterizations in arXiv:1304.0901
J/ψ / D0 Ratios
] c [MeV/T
pTransverse momentum 0 1 2 3 4 5 6 7 8
310×
)0(Dσ
) /
ψ(J
/σ
0
1
2
3
4
5
6
7
8
9
103−10×
= 110 GeV pArNNs LHCb preliminary
Rapidity y2 2.5 3 3.5 4 4.5
)0(Dσ
) /
ψ(J
/σ
0
1
2
3
4
5
6
7
8
9
103−10×
= 110 GeV pArNNs LHCb preliminary
G. Graziani slide 22 PBC, Nov 21 2017
SMOG luminosity determination LHCb-CONF-2017-002
Gas target density not precisely knownè using p-e− elastic scatteringdistinct signature with single low-p andvery-low-pT electron track, and nothingelseresidual background charge symmetricto good approximation è data-drivenbackground subtraction
p [MeV/c]5000 10000 15000
Can
dida
tes
per
260
MeV
/c
1000
2000
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5000
candidates-e
candidates+e
LHCb Preliminary
p [MeV/c]5000 10000 15000
Can
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tes
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/c
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candidates (Bkg Sub.)-e
Simulation (normalized)
LHCb Preliminary
[MeV/c]T
p0 50 100
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per
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/c
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[MeV/c]T
p0 50 100
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dida
tes
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/c
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1200
1400
1600
1800LHCb Preliminary
Very good agreement with simulation of sin-gle scattered electrons
L = 0.443± 0.011± 0.027 nb−1
equivalent gas pressure is 2.4×10−7 mbar, inagreement with the expected level in SMOG6% systematic from absolute reconstructionefficiency
G. Graziani slide 23 PBC, Nov 21 2017
Result for p cross section, compared with EPOS LHCLHCb-CONF-2017-002
[GeV/c]T
p0 1 2 3 4
]2/G
eV2
b c
µ [T
X)/
dpdp
p(σ2 d
19−10
17−10
15−10
13−10
11−10
9−10
7−10
5−10
3−10
1−10
10
210 x (12.0 < p < 14.0 GeV/c)-010
x (14.0 < p < 16.2 GeV/c)-110
x (16.2 < p < 18.7 GeV/c)-210
x (18.7 < p < 21.4 GeV/c)-310
x (21.4 < p < 24.4 GeV/c)-410
x (24.4 < p < 27.7 GeV/c)-510
x (27.7 < p < 31.4 GeV/c)-610
x (31.4 < p < 35.5 GeV/c)-710
x (35.5 < p < 40.0 GeV/c)-810
x (40.0 < p < 45.0 GeV/c)-910
x (45.0 < p < 50.5 GeV/c)-1010
x (50.5 < p < 56.7 GeV/c)-1110
x (56.7 < p < 63.5 GeV/c)-1210
x (63.5 < p < 71.0 GeV/c)-1310
x (71.0 < p < 79.3 GeV/c)-1410
x (79.3 < p < 88.5 GeV/c)-1510
x (88.5 < p < 98.7 GeV/c)-1610
x (98.7 < p < 110.0 GeV/c)-1710
LHCb Preliminary
Result for prompt production(excluding weak decays of hy-perons)
The total inelastic cross sectionis also measured to be
σLHCbinel = (140± 10) mb
The EPOS LHC prediction[T. Pierog at al, Phys. Rev. C92 (2015), 034906]
is 118 mb, ratio is 1.19± 0.08.
G. Graziani slide 24 PBC, Nov 21 2017