SMOG: experimental results - Elisabeth Maria Niel on behalf of the LHCb collaboration
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SMOG: experimental results Elisabeth Maria Niel on behalf of the LHCb collaboration École polytechnique fédérale de Lausanne LHCP, 2-5 May 2022
The LHCb detector 2 ! acceptance b [IJMPA 30 (2015) 1530022] Ø Excellent performances [JINST 3 (2008) S08005] Muon system Ø It is a “charm factory”: for collisions, μ identification ε(μ→μ) ~ 97 %, mis-ID ε(π→μ) ~ 1-3 % § 4 × 10!" #" #$ luminostiy for Run 2: RICH detectors the rate of c ̅ pairs is 0.96 MHz K/π/p separation 10-250mrad ε(K→K) ~ 95 %, § rate of Λ&% seen by the LHCb detector mis-ID ε(π→K) ~ 5 % Vertex Detector ~12m ~602 Hz reconstruct vertices decay time resolution: 45 fs Ø Unique system to inject gas (SMOG) originally IP resolution: 20 μm ~20m designed for luminosity measurements. Re-used to transform LHCb in a fixed-target 10-300mrad experiment. [JINST 9 (2014) P12005] m Bea Ø Injection valve: Tracking system: Target TT and OT momentum resolution Calorimeters (ECAL, Dipole Magnet Δp/p = 0.5%–1.0% HCAL) bending power: 4 Tm (5 GeV/c – 100 GeV/c) energy measurement e/γ identification ΔE/E = 1 % ⨁10 %/√E (GeV) Single arm forward spectrometer with excellent vertexing, tracking, PID (acceptance 2 < < 5) Elisabeth Niel - LHCP 2022
SMOG 3 • SMOG: System for Measuring Overlap with Gas • A noble gas (He, Ne, Ar) at ~ 2 ×10!" mbar pressure injected into the LHC vacuum around the LHCb interaction region • Energy between SPS and RHIC • Rapidity: −3.0 < ∗ < 0 y = 3.5 Bjorken x = fraction of proton momentum carried by the quark y=5 y = 2.5 arXiv:1612.05741 y = 3.5 With intrinsic charm Phys. Rev. D 75, 054029 y=5 y = 2.5 With no • Access nPDF anti-shadowing region intrinsic charm • Can probe intrinsic charm content of nucleon • Important input for astrophysics measurements LHCb LHCb ( ) ℎ ( ) Elisabeth Niel - LHCP 2022
SMOG pollution 4 • Data are taken simultaneously with collisions at 5 TeV, no special runs pollution from pp collisions « ghost charges ». v pp and p-Gas data are taken at the same time alternating full and empty bunches. v Some debunched protons from the previous beam go to the following bunch which is supposed to be empty. Cleaning using the event topology: Z-coordinate and number of hits pile-up stations PU stations https://cds.cern.ch/record/2720461. VELO pollution Beam 1 SMOG VELO Beam 1 Beam 2 gas Debunched Beam 1 Empty protons pp empty p-empty = −1000 = −315 = 500 SMOG Pollution from = 0 previous bunch = −220 Elisabeth Niel - LHCP 2022
Physics results with SMOG 5 Previous SMOG results: 1. Charm production in pAr, pHe collisions Phys. Rev. Lett. 122 (2019) 132002 2. Prompt antiproton in pHe collisions at 110 GeV Phys. Rev. Lett. 121 (2018) 222001 New Results : 1. Charmonia production in pNe collisions at !! = 68.5 GeV LHCb-PAPER-2022-014 2. D" and / production in PbNe collisisons at !! = 68.5 GeV LHCb-PAPER-2022-012 3. Detached antiproton production in pHe collisions at !! = 110 GeV LHCb-PAPER-2022-006 New technical publications 1. A Neural-Network-defined Gaussian Mixture Model for PID with SMOG data JINST 17 (2022) P02018 2. Centrality determination in heavy-ion collisions with the LHCb detector CERN-LHCb-DP-2021-002 Elisabeth Niel - LHCP 2022
Charm production as a probe for QCD 6 Charmonium production 1. It’s a smoking gun of QGP production via the color screen mechanism T. Matsui, H. Satz, Physics Letters B 178 (1986), no. 4 . Phys.Rev.D 64 (2001) 094015 / suppression has been studied in several fixed-target experiment, however the underlying mechanism is still not fully understoodà new measurements in different colliding systems are fundamental to constraint cold nuclear matter effects 2. Other charmonium states also affected : (2 ) and % with lower binding energy (suppressed at lower temperature). For / produced from excited states à sequential suppression. 3. Suppression compensated by statistical recombination at high '' Why Open Charm? 1. ( open charm, not affected by QGP and gives an estimate of the total amount of ̅ pairs 2. Compare the ratio / to ( in pNe and PbNe systems 3. Cross-section and asymmetry relevant to study the nucleon content Today’s measurement with SMOG LHCb data: 1. / cross-section (integrated and as a function of ) and ∗ ) 2. / / (2 ) ratio using di-muon decay 3. / / ( ratio , using ( → # & Elisabeth Niel - LHCP 2022
Charmonium production in pNe 7 Cross section defined as: Number of Ø / and 2 efficiency reconstructed via di-muon corrected events Preliminary after selections decay: #$% = 4 542 / → & ' #$% = 76 2 → & ' luminosity Atomic number Ne Branching ratio Ø Results: 400 300 [nb/nucleon] dσ(J/ψ ) [nb/nucleon] LHCb LHCb • HELAC-ONIA using CT14NLO [GeV/ c ] 350 sNN = 68.5 GeV p Ne 250 sNN = 68.5 GeV p Ne 300 LHCb data HELAC-Onia LHCb data and nCTEQ15 under shoot the 250 Vogt no IC Vogt 1% IC 200 HELAC-Onia data Vogt no IC dσ(J/ψ ) 200 150 Vogt 1% IC dy* • Good agreement with T 150 dp 100 100 predictions with (1%) Intrinsic 50 50 Charm (IC) and without it 0 0 −2 −1.5 −1 −0.5 0 0 2 4 6 8 y* p [GeV/c ] T Elisabeth Niel - LHCP 2022
Charmonium production pNe 8 / cross section measurement: σ(p N → J/ψ X) [nb/nucleon] LHCb sNN = 68.5 GeV p Ne • Total cross-section: extrapolation to full phase space sNN = 86.6 GeV p He using Pythia8+CT09MCS PDF 103 • Power-law dependency with $$ found Ratio / / first measurement in SMOG: 102 other experiments In line with other measurements for different values of target atomic mass number (A): 102 sNN [GeV] [%] 2.2 sNN = 68.5 GeV p Ne LHCb BRψ(2S)→µ+µ- σψ(2S) LHCb data 2 BRJ/ ψ→µ+µ- σJ/ ψ Candidates / (10 MeV/c 2) 35 LHCb 30 1.8 sNN = 68.5 GeV p Ne 25 1.6 20 15 1.4 NA51 p-p, d, sNN = 29.1 GeV NA50 p-Be, Al, Cu, Ag, W, sNN = 29.1 GeV 10 NA50 p-Be, Al, Cu, Ag, W, Pb, sNN = 27.4 GeV 1.2 E771 p-Si sNN = 38.8 GeV 5 E789 p-Au sNN = 38.8 GeV 0 1 3600 3700 3800 m(µ +µ -) [MeV/c2] Elisabeth Niel - LHCP 2022 1 10 102 A
! and / in PbNe collisions 9 • First measurement of / and in fixed target nucleus-nucleus collisions • Centrality determined by energy deposit in electromagnetic calorimeter arXiv:2111.01607 • The ratio of J/ψ over ( is evaluated integrated and binned in and ) . • Luminosity measurement on-going, no absolute cross section available yet • Ratio integrated: −3 −3 10 ×10 40 ×10 σJ/ ψ/ σD0 σJ/ ψ/ σD0 9 sNN = 68.5 GeV PbNe sNN = 68.5 GeV PbNe LHCb LHCb 35 stat. + uncorr. syst. stat. + uncorr. syst. 8 corr. syst. 30 corr. syst. 7 25 6 20 5 Ø No dependence on rapidity 4 15 3 10 Ø Strong dependence on % 2 5 1 0 −2 −1.5 −1 −0.5 0 0 0 2 4 6 8 LHCb-PAPER-2022-011 y* p [GeV/c ] T In preparation Elisabeth Niel - LHCP 2022
Charm in pNe vs PbNe 10 • Evaluate suppression as a function of the number of binary nucleon-nucleon collisions %,-- (estimated from Glauber model to data) • pNe collisions = very peripheral PbNe collisions • Ratio for PbNe and pNe vs %,-- fitted with a power law: • assuming • / supressed by CNM + QGP ! = 0.82 ± 0.07 σJ/ ψ/ σD0 sNN = 68.5 GeV LHCb 10−2 PbNe α' = 0.82 ± 0.07 Conclusions: / suppression is consistent with CNM without additional QGP effects 1 10 102 N coll Elisabeth Niel - LHCP 2022
Detached antiproton in pHe collisions at 110 GeV 11 K component in Space-borne experiments PAMELA and AMS-02 improved measurements of the abundance of the cosmic rays, which is sensitive to a possible dark matter contribution K production cross-sections in the spallation of cosmic rays in the interstellar medium àRequires knowledge of the Ø Uncertainty still dominated by XS : Ø The ratio /. is predicted to increase as a function of '' Ratio secondary/prompt production Phys. Rev. Research 2, 023022 45 % JCAP 02 (2017) 048 Residuals predictions vs data A production Phys. Rev. Lett. 121 (2018) 222001 Previous SMOG measurement à prompt (produced directly at the primary vertex) NEW ̅ production from anti-hyperons weak decays (non-prompt) Elisabeth Niel - LHCP 2022
Detached antiproton in pHe collisions at 110 GeV 12 Ø Mesure detached A in pHe collisions and compare to the prompt A A decays and inclusively à ratio as a cross check (better constrained) Ø Measure it exclusively exploting Λ Exclusive: Inclusive: Ø 6. 5 TeV proton beam on He target à '' = 110 GeV , with a luminosity of 0.5 #$ Ø The detached decay vertex and the invariant-mass resolution + decay kinematics (asymmetry momenta) allow identificaiton of ̅ arXiv:2205.09009 arXiv:2205.09009 50.7 k events Elisabeth Niel - LHCP 2022
Detached antiproton in pHe collisions at 110 GeV 13 arXiv:2205.09009 Ø Most generators undershoot data and do not describe the arXiv:2205.09009 momentum dependance Ratio is predicted reliably and used to check the consistency of the two complementary approaches Preliminary Conlusions: Ø Most generators Ø Found increased anti-hyperon contribution wrt undershoot data at previous measurement at ,, = 10 GeV low momentum, underestimated in most of hadronic production however general models used in cosmic ray physics behavior reproduced Ø -! dependance as fct of transverse momenutm also need to be included in the models These results are a valuable input to improve the predictions for the secondary ̅ cosmic flux
SMOG2 14 • Upgraded SMOG system with storage cell placed upstream nominal IP at z [-500,-300] mm, with dedicated Gas Feed System. • Gas density increased of 2 orders of magnitude à higher luminosity • Gas target possible: . , . , , . , . , , , , • Separated luminous region from pp allowing for simultaneous data- taking à more statistics Elisabeth Niel - LHCP 2022
Conclusions 15 Ø SMOG data have produced unique results and more results are to come! Ø Today : 1. Charmonia production in pNe at 68.5 GeV 2. Open charm and charmonia production PbNe at 68.5 GeV 3. Detached ̅ production in pHe at 110 GeV Ø Future: charm baryons (Λ&% and Ξ%&) polarization, production cross-section and asymmetry Ø SMOG2 successfully installed, first runs are coming soon! Beam is back! LHCb Control Room Elisabeth Niel - LHCP 2022
Centrality determination in PbNe 16 • The centrality of a nucleus-nucleus à overlap region between the nuclei where the nucleons are colliding. • MC Glauber model used to to isolate the hadronic PbNe PbPb part and subsequently define the centrality classes • Proxy: energy deposit in the ECAL (VELO clusters saturates) PbNe PbPb CERN-LHCb-DP-2021-002 https://arxiv.org/pdf/2111.01607.pdf Elisabeth Niel - LHCP 2022
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