Antiproton production in p-He collisions, and more, at LHCb LHCb on - - PowerPoint PPT Presentation
Antiproton production in p-He collisions, and more, at LHCb LHCb on a Space Mission He at 6.5 TeV rest proton antiproton Giacomo Graziani (INFN Firenze) on behalf of the LHCb Collaboration ICRC 2017, Busan, Korea July 15, 2017 The LHCb
6.5 TeV proton He at rest antiproton
Giacomo Graziani (INFN Firenze)
ICRC 2017, Busan, Korea July 15, 2017
LHCb is the experiment devoted to heavy flavours at the LHC Focused on CP violation and rare signatures in b and c decays Exploiting LHC as the biggest b and c fac- tory on earth Detector requirements: Forward geometry optimize acceptance for bb pairs Tracking : best possible proper time and momentum resolution Particle ID : excellent capabilities to select exclusive decays Trigger : high flexibility and bandwidth (up to 15 kHz to disk) ➨ allowed to widen our physics program to include hadron spectroscopy, EW physics, kaon physics, heavy ion physics (pPb and PbPb collisions) ...
slide 2 ICRC 2017
LHCb is the LHC experiment with “fixed-target like” geometry very well suited for...fixed target physics!
JINST 3, (2008) S08005 Int.J.Mod.Phys.A30 (2015) 1530022
The System for Measuring Overlap with Gas (SMOG) allows to inject small amount of noble gas (He, Ne, Ar, ...) inside the LHC beam around (∼ ±20 m) the LHCb collision region Expected pressure ∼ 2 × 10−7 mbar Originally conceived for the luminosity determination with beam gas imaging
JINST 9, (2014) P12005
Became the LHCb internal gas target for a rich and var- ied fixed target physics program
slide 3 ICRC 2017
Fixed target collisions allow to study exclusive particle production at the energy scale of ∼ 100 GeV, with access to large x in the target; can provide valuable inputs for modeling cosmic ray showers in the atmosphere and in the cosmos, in particular for antimatter production AMS02 results provide unprecedented accuracy for measurement of p/p ratio in cosmic rays at high energies
PRL 117, 091103 (2016)
hint for a possible excess, and milder en- ergy dependence than expected prediction for p/p ratio from spallation
medium (H and He) is presently limited by uncertainties on p production cross- sections, particularly for p-He no previous measurement of p production in p-He, current predictions vary within a factor 2 the LHC energy scale and LHCb +SMOG are very well suited to perform this mea- surement
Giesen et al., JCAP 1509, 023 (2015)
slide 4 ICRC 2017
JINST 3, (2008) S08005 Int.J.Mod.Phys.A30 (2015) 1530022
p [GeV/c]
20 40 60 80 100
[GeV/c]
T
p
0.5 1 1.5 2 2.5 3 3.5 4 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 =5 η = 4 . 5 η
LHCb Preliminary
LHCb-CONF-2017-002
Total acceptance × reconstruction efficiency for antiprotons Tracking efficiency estimated from simulation, validated on (pp) data
slide 5 ICRC 2017
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 events Exploit excellent particle identification (PID) capabilities in LHCb to count antiprotons in (p, pT) bins within the kinematic range 12 < p < 110 GeV /c, pT > 0.4 GeV /c Exploit excellent vertexing capabilities to separate prompt and detached components. Only the prompt component included in this preliminary result (analysis of component from hyperon decays ongoing). Residual detached component estimated to be (2.6 ± 0.6)% and subtracted Background from gas contamination measured to be 0.6 ± 0.2%
Data p 21.4 - 24.4 pt 1.2- 1.5
DLL (p -K)
100 200 ) π DLL (p -
50 100 150 200
LHCb Preliminary
100 200
50 100 150 200 20 40 60 80 100 120 140
Template for p
100 200
50 100 150 200 100 200 300 400 500 600 700 800 900
π Template for
100 200
50 100 150 200 50 100 150 200 250
Template for K
100 200
50 100 150 200 10 20 30 40 50 60
Template for ghost
slide 6 ICRC 2017
Gas target density not precisely known, using p-e− elastic scattering Pro: LHCb sees the purely elastic regime: θ > 10mrad ➨ ϑs < 29 mrad, Q2 < 0.01 GeV2 ➨ cross-section very well known distinct signature with single low-p and very low pT electron track, and nothing else background events mostly expected from very soft collisions, where candidate comes from γ conversion or pion from central exclusive pro- duction event ➨ background expected to be charge symmetric, can use “single positrons” to model it in data
SPD hits
5 10 15 20
scattered electron candidates
1000 2000 3000 4000 5000 6000 7000 8000 9000
candidates
candidates
+
e
LHCb Preliminary
LHCb-CONF-2017-002
Cons: cross-section is small (order 100 µb, 3 orders of magnitude below hadronic cross section) electron has very low momentum and showers through beam pipe/detectors ➨ low acceptance and reconstruction efficiency
slide 7 ICRC 2017
slide 8 ICRC 2017
LHCb-CONF-2017-002 p [MeV/c]
5000 10000 15000
Candidates per 260 MeV/c
1000 2000 3000 4000 5000
candidates
candidates
+
e
LHCb Preliminary
p [MeV/c]
5000 10000 15000
Candidates per 260 MeV/c
500 1000 1500 2000 2500 3000 candidates (Bkg Sub.)
Simulation (normalized) LHCb Preliminary
[MeV/c]
T
p
50 100
Candidates per 2.4 MeV/c
500 1000 1500 2000 2500 LHCb Preliminary
[MeV/c]
T
p
50 100
Candidates per 2.4 MeV/c
200 400 600 800 1000 1200 1400 1600 1800 LHCb Preliminary
Very good agreement with simulation of single scat- tered electrons Data confirm charge sym- metry of background L = 0.443 ± 0.011 ± 0.027 nb−1 Systematic from variation of selection cuts, largest dependence is on azimuthal angle equivalent gas pressure is 2.4 × 10−7 mbar, in agreement with the expected level in SMOG
slide 9 ICRC 2017
LHCb-CONF-2017-002
24.7 13.3 27.6 19.1 9.5 9.6 17.5 8.2 8.8 7.9 19.9 22.2 17.0 12.4 9.8 8.5 9.4 9.5 15.0 9.7 9.4 10.2 10.4 15.7 10.2 10.9 10.8 10.7 8.1 9.3 7.9 8.5 8.6 8.0 13.6 23.3 10.7 12.2 9.5 9.8 13.9 14.7 9.6 9.8 8.2 8.5 7.9 8.0 8.1 15.1 21.0 10.4 9.4 11.1 9.7 10.6 17.3 13.7 10.8 11.7 11.4 9.8 9.9 9.2 11.4 11.1 12.1 9.6 9.6 10.4 9.7 13.4 12.4 11.0 10.1 8.7 8.5 10.3 9.8 15.8 9.8 9.2 9.2 9.2 9.5 12.8 11.6 10.7 12.6 17.2 17.5 11.6 12.9 10.7 9.1 12.5 10.3 9.4 10.1 9.4 9.4 9.4 9.5 9.5 10.2 14.0 20.0 25.7 20.6 17.0 16.9 14.5 13.0 12.0 15.8 11.1 10.8 10.8 10.8 11.3 11.2 10.5 12.2 12.3 12.5 25.1 25.8 24.9 24.4 20.9 20.6 20.1 19.6 20.4 22.2 28.6
2
10
T
1 5 10 15 20 25 = 5 η = 4 . 5 η
LHCb Preliminary
dominated by systematics largest correlated uncertainty is the 6% from normalization largest uncorrelated uncertainty from PID analysis
slide 10 ICRC 2017
LHCb-CONF-2017-002
T
1 2 3 4
2
2
T
2
19 −
10
17 −
10
15 −
10
13 −
10
11 −
10
9 −
10
7 −
10
5 −
10
3 −
10
1 −
10 10
2
10
x (12.0 < p < 14.0 GeV/c)
10 x (14.0 < p < 16.2 GeV/c)
10 x (16.2 < p < 18.7 GeV/c)
10 x (18.7 < p < 21.4 GeV/c)
10 x (21.4 < p < 24.4 GeV/c)
10 x (24.4 < p < 27.7 GeV/c)
10 x (27.7 < p < 31.4 GeV/c)
10 x (31.4 < p < 35.5 GeV/c)
10 x (35.5 < p < 40.0 GeV/c)
10 x (40.0 < p < 45.0 GeV/c)
10 x (45.0 < p < 50.5 GeV/c)
10 x (50.5 < p < 56.7 GeV/c)
10 x (56.7 < p < 63.5 GeV/c)
10 x (63.5 < p < 71.0 GeV/c)
10 x (71.0 < p < 79.3 GeV/c)
10 x (79.3 < p < 88.5 GeV/c)
10 x (88.5 < p < 98.7 GeV/c)
10 x (98.7 < p < 110.0 GeV/c)
10
LHCb Preliminary
Result for prompt production (excluding weak decays of hy- perons) The total inelastic cross section is also measured to be σLHCb
inel
= (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.
slide 11 ICRC 2017
LHCb-CONF-2017-002
DATA / PREDICTION
1 2 3 4 data/ prediction 0.5 1 1.5 2 2.5 3
12.0 < p < 14.0 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
14.0 < p < 16.2 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
16.2 < p < 18.7 GeV/c
LHCb Preliminary 1 2 3 4
data/ prediction 0.5 1 1.5 2 2.5 3
18.7 < p < 21.4 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
21.4 < p < 24.4 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
24.4 < p < 27.7 GeV/c
LHCb Preliminary 1 2 3 4
data/ prediction 0.5 1 1.5 2 2.5 3
27.7 < p < 31.4 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
31.4 < p < 35.5 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
35.5 < p < 40.0 GeV/c
LHCb Preliminary 1 2 3 4
data/ prediction 0.5 1 1.5 2 2.5 3
40.0 < p < 45.0 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
45.0 < p < 50.5 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
50.5 < p < 56.7 GeV/c
LHCb Preliminary 1 2 3 4
data/ prediction 0.5 1 1.5 2 2.5 3
56.7 < p < 63.5 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
63.5 < p < 71.0 GeV/c
LHCb Preliminary 1 2 3 4 0.5 1 1.5 2 2.5 3
71.0 < p < 79.3 GeV/c
LHCb Preliminary [GeV/c]
T
p 1 2 3 4 data/ prediction 0.5 1 1.5 2 2.5 3
79.3 < p < 88.5 GeV/c
LHCb Preliminary [GeV/c]
T
p 1 2 3 4 0.5 1 1.5 2 2.5 3
88.5 < p < 98.7 GeV/c
LHCb Preliminary [GeV/c]
T
p 1 2 3 4 0.5 1 1.5 2 2.5 3
98.7 < p < 110.0 GeV/c
LHCb Preliminary
Trasverse Momentum (GeV/c)
EPOS LHC EPOS 1.99 QGSJETII-04 HIJING 1.38
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 and QGSJET-IIm (low energy extension
Many thanks to T. Pierog for his advice with EPOS/CRMC!
slide 12 ICRC 2017
We plan to extend the study to p produced by hyperon decays (accounting for 20-30%
decays of Λ
]
2
c Invariant Mass [MeV/
+
π p 1100 1110 1120 1130
2
c Candidates / 0.6 MeV/ 100 200 300 ]
2
c Invariant Mass [MeV/
+
π p 1100 1110 1120 1130
2
c Candidates / 0.6 MeV/ 100 200 300
2
c 0.03 MeV/ ± = 1115.75 µ
2
c 0.33 MeV/ ± = 1.23 σ 36 ± N = 1177
LHCb
= 0.9 TeV s
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) ➨ scaling violation can be constrained production of pions and kaons is also being measured ➨ positron production. Ratios of particle species, not affected by uncertainty on luminosity, can provide precise constraints to soft QCD models investigating our potential for antinuclei d, t and 3He RICH can actively identify d from p 36 GeV /c and t,3He from 54 GeV /c. dE/dx and time-of-flight information from tracking detectors at low momentum
slide 13 ICRC 2017
Exclusive production of charm states is a specialty of LHCb
]
2
c ) [MeV/
+
π
1800 1820 1840 1860 1880 1900 1920 1940
)
2
c Candidates / (5 MeV/
100 200 300 400 500 600 700
= 87 GeV pHe
NN
s
LHCb preliminary
D0 → K−π+
]
2
c ) [MeV/
+
µ m(
2950 3000 3050 3100 3150 3200
)
2
c Candidates / (10 MeV/
20 40 60 80 100
= 87 GeV pHe
NN
s
LHCb preliminary
J /ψ → µ+µ− In fixed target mode, access the large-x (target fragmenta- tion) region, where charm PDF is affected by antishadow- ing and possibly intrinsic charm (IC) effects. Important for high-energy neutrino astrophysics: back- ground for the ICECUBE experiment is dominated by charm production in atmospheric showers
2 [GeV cm-2 s-1 sr-1]
Eµ [GeV]
10-10 10-9 10-8 10-7 10-6 103 104 105 106
I n t r i n s i c C h a r m dotted grey: Conv. Atm. µ solid grey: Conv. Atm. µ + BERSS solid black: Conv. Atm. µ + Intrinsic Charm (H3A) + BERSS IceCube astrophysical flux IceCube µ
Laha and Brodsky, arXiv:1607.08240
slide 14 ICRC 2017
LHCb-CONF-2017-001
x-Feynman distribution for D0 and J /ψ, compared to Pythia8 prediction
F
Feynman-x x
0.25 − 0.2 − 0.15 − 0.1 − 0.05 −
F
/dx
D
dN
0.05 0.1 0.15 0.2 0.25
6
10 ×
= 110 GeV pAr
NN
s
LHCb preliminary
sinh(y*)
NN
s
D
M = 2
F
x
F
Feynman-x x
0.45 − 0.4 − 0.35 − 0.3 − 0.25 − 0.2 − 0.15 − 0.1 − 0.05 −
F
/dx
ψ J/
dN
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
3
10 ×
= 110 GeV pAr
NN
s
LHCb preliminary
sinh(y*)
NN
s
ψ J/
M = 2
F
x
Obtained from the first small (few nb−1) p-Ar data sample acquired in 2015 ∼ 6500 D0 and 500 J /ψ Result limited by statistics, but demonstrates the potential for unique measurements Differential shapes can already constrain models with IC
slide 15 ICRC 2017
thanks to O. Adriani, L. Bonechi, F. Donato and A. Tricomi for proposing this measurement
slide 16 ICRC 2017
slide 17 ICRC 2017
slide 18 ICRC 2017
Current analysis limited to “prompt” component (direct production and p from strong resonance decays) Can be distinguished from p produced by weak decays of hyperons and secondary interactions using the excellent LHCb vertexing capabilities
JINST 9 (2014) P09007
slide 19 ICRC 2017
]
c [GeV
T
p 1/ 0.5 1 1.5 2 2.5 3 m] µ resolution [
x
IP 10 20 30 40 50 60 70 80 90 100
T
p = 11.6 + 23.4/ σ 2012 data,
T
p = 11.6 + 22.6/ σ Simulation,
JINST 9 (2014) P09007
slide 20 ICRC 2017
Residual vacuum in LHC is not so small (∼ 10−9 mbar ) compared to SMOG pressure Can be a concern, especially for heavy contaminants (larger cross section than He), and beam-induced local outgassing Direct measurement in data: about 15% of delivered protons on target acquired before He injection (but with identical vacuum pumping configuraton)
PV Track Multiplicity
5 10 15 20 25 30 35 40
fraction of candidates
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 vacuum events is lower than in He events, but has longer tails ➨ confirm findings from Rest Gas Analysis that resid- ual vacuum is mostly H2, with small heavy contaminants
slide 21 ICRC 2017
LHCb-CONF-2017-002
Statistical: Yields in data/PID calibration 0.7 − 10.8% (< 3% for most bins) Normalization 2.5% Correlated Systematic: Normalization 6.0% GEC and PV cut 0.3% PV reco 0.8% Tracking 2.2% Residual Vacuum Background 0.1% Non-prompt background 0.3 − 0.7% PID 1.2 − 5.0% Uncorrelated Systematic: Tracking 3.2% IP cut efficiency 1.0% PID 0 − 26% (< 10% for most bins) MC statistics 0.8 − 15% (< 4% for pT < 2 GeV/c)
slide 22 ICRC 2017
F
0.2 − 0.1 −
2
2
T
2
1 −
10 1 10
2
10
12<p<14 GeV/c 14<p<16.2 GeV/c 16.2<p<18.7 GeV/c 18.7<p<21.4 GeV/c 21.4<p<24.4 GeV/c 24.4<p<27.7 GeV/c 27.7<p<31.4 GeV/c 31.4<p<35.5 GeV/c 35.5<p<40 GeV/c 40<p<45 GeV/c 45<p<50.5 GeV/c 50.5<p<56.7 GeV/c 56.7<p<63.5 GeV/c 63.5<p<71 GeV/c 71<p<79.3 GeV/c 79.3<p<88.5 GeV/c 88.5<p<98.7 GeV/c 98.7<p<110 GeV/c EPOSLHC
slide 23 ICRC 2017
EPOS LHC PRC92, 034906 (2015)
p [GeV/c] 20 40 60 80 100 [GeV/c]
T
p
0.5 1 1.5 2 2.5 3 3.5 4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
LHCb Preliminary
EPOS1.99
σ /
LHCb
σ
QGSJET-II-04 PRD83, 014018 (2011)
p [GeV/c] 20 40 60 80 100 [GeV/c]
T
p
0.5 1 1.5 2 2.5 3 3.5 4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
LHCb Preliminary
QGSJETII
σ /
LHCb
σ
HIJING 1.38 Comp. Phys. Comm. 83, 307 (1994)
p [GeV/c] 20 40 60 80 100 [GeV/c]
T
p
0.5 1 1.5 2 2.5 3 3.5 4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
LHCb Preliminary
HIJING
σ /
LHCb
σ
QGSJET-IIm Astr. J. 803:54 (2015)
p [GeV/c] 20 40 60 80 100 [GeV/c]
T
p
0.5 1 1.5 2 2.5 3 3.5 4 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
LHCb Preliminary
QGSJETIIm
σ /
LHCb
σ
slide 24 ICRC 2017