AT THE LHC Mariola Kusek-Gawenda INSTITUTE OF NUCLEAR PHYSICS - PowerPoint PPT Presentation

MESON2018 γγ FUSION IN HEAVY ION UPC I MPORTANCE OF MESONS EPA IN L IGHT - BY -L IGHT SCATTERING γγ SCATTERING E > 5 G E V E < 5 G E V IN ULTRAPERIPHERAL LEAD - LEAD COLLISIONS E < 2 G E V C ONCLUSION AT THE LHC Mariola Kłusek-Gawenda INSTITUTE OF NUCLEAR PHYSICS POLISH ACADEMY OF SCIENCE Kraków, Poland γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 1 / 22

MESON2018 γγ FUSION IN HEAVY ION UPC EPA γγ SCATTERING E > 5 G E V E < 5 G E V E < 2 G E V C ONCLUSION U LTRA P ERIPHERAL C OLLISIONS M. K-G, P. Lebiedowicz, A. Szczurek, ➳ Light-by-light scattering in ultraperipheral Pb-Pb collisions at energies available at the CERN Large Hadron Collide, Phys. Rev. C93 (2016) 044907, M. K-G, W. Schäfer, A. Szczurek, ➳ Two-gluon exchange contribution to elastic γγ → γγ scattering and production of two-photons in ultraperipheral ultrarelativistic heavy ion and proton-proton collisions, Phys. Lett. B761 (2016) 399, M. K-G, R. McNulty, R. Schicker, A. Szczurek, ➳ Measurements of light-by-light scattering in UPC of heavy ions at the LHC - smaller diphoton collision energies, in preparation. γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 2 / 22

EPA N UCLEAR C ROSS S ECTION MESON2018 γγ FUSION IN HEAVY ION UPC EPA A A A A A A γγ SCATTERING γ γ γ γ γ γ π 0 E > 5 G E V E < 5 G E V R γ γ E < 2 G E V γ γ γ γ γ C ONCLUSION π 0 γ A A A A A A C ONTINUUM R ESONANCES B ACKGROUND � N ( ω 1 , b 1 ) N ( ω 2 , b 2 ) S 2 σ A 1 A 2 → A 1 A 2 γγ = abs ( b ) σ γγ → γγ ( W γγ ) × b 1 b 2 W γγ d 2 b d b x d b y 2 d W γγ d Y γγ × b γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 3 / 22

E > 5 G E V γγ SCATTERING MESON2018 γ − γ ELASTIC SCATTERING γγ FUSION IN HEAVY ION UPC W ELL - KNOWN EPA B OXES γγ SCATTERING E > 5 G E V γ γ γ γ W E < 5 G E V E < 2 G E V W W C ONCLUSION γ γ γ γ W W E ADD VDM-R EGGE 2- GLUON C ONTRIBUTION E XCHANGE γ γ γ γ V . ρ, ω, φ 16 diagrams g g IP, IR ⇒ ⇒ γ γ γ γ V γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 4 / 22

E > 5 G E V γγ SCATTERING MESON2018 B OXES Γ Γ Γ Γ � 7 10 (pb) γγ FUSION IN 6 HEAVY ION UPC 10 Γ Γ Γ Γ σ W W Γ Γ W 5 W 10 W Γ γ γ → γ γ W W W EPA W Γ 4 10 total Γ Γ Γ Γ leptons γγ SCATTERING 3 10 quarks E > 5 G E V Γ Γ Γ Γ 2 W-bosons 10 Γ E < 5 G E V W W W W E < 2 G E V Γ W 10 W W W W C ONCLUSION Γ 1 Γ Γ Γ Γ Γ -1 10 Γ Γ Γ Γ Γ W W Γ -2 10 W W W W W W W -3 10 -3 -2 -1 2 3 10 10 10 1 10 10 10 Γ W W W Γ Γ Γ Γ Γ s (GeV) We have compared our results with: Γ Γ Γ W ◮ Γ Γ Jikia et al. (1993), Γ Γ W W W W ◮ Γ Bern et al. (2001), Γ W ◮ Bardin et al. (2009). Γ Γ Γ Bern et al. consider QCD and QED corrections Γ Γ Γ Γ Γ F F Γ (two-loop Feynman diagrams) to the one-loop F F F F F F F fermionic contributions in the ultrarelativistic limit Γ F F F Γ Γ Γ Γ Γ s , | ˆ u | ≫ m 2 ( ˆ t | , | ˆ f ). The corrections are quite small Fermionic box LO QED - FormCalc . numerically. The one-loop W box diagram - LoopTools . γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 5 / 22

E > 5 G E V γγ SCATTERING E XPERIMENTAL IDENTIFICATION OF PROCESSES ? MESON2018 ✔ boxes γγ FUSION IN HEAVY ION UPC ✔ VDM-Regge ✔ 2-gluon exchange EPA γγ SCATTERING E > 5 G E V W = 10 GeV W = 50 GeV W = 200 GeV E < 5 G E V E < 2 G E V -1 -1 -1 C ONCLUSION (nb/GeV) 10 (nb/GeV) 10 (nb/GeV) 10 2-gluon exchange, n =4 2-gluon exchange, n =4 2-gluon exchange, n =4 f f f boxes m =0.75 GeV boxes m =0.75 GeV boxes m =0.75 GeV g g g -2 -2 -2 10 10 10 VDM-Regge m =0 VDM-Regge m =0 VDM-Regge m =0 g g g W=10 GeV W=50 GeV W=200 GeV γ γ γ t t t /dp -3 /dp -3 /dp -3 10 10 10 γ γ γ γ γ γ → → → 10 -4 10 -4 10 -4 γ γ γ γ γ γ σ σ σ d d d -5 -5 -5 10 10 10 -6 -6 -6 10 10 10 10 -7 10 -7 10 -7 -8 -8 -8 10 10 10 0 1 2 3 4 5 0 1 2 3 4 5 0 5 10 15 20 p p p t t t γ γ γ γ − γ Collider (the International e + e − Linear Collider) ? γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 6 / 22

E > 5 G E V γγ SCATTERING MESON2018 AA → AA γγ - FORM FACTOR γγ FUSION IN HEAVY ION UPC ➯ realistic EPA ➯ monopole γγ SCATTERING 6 10 (pb/GeV) F , F E > 5 G E V monopole realistic boxes E < 5 G E V 5 E < 2 G E V 10 VDM-Regge γ γ γ γ C ONCLUSION )/dM s =5.5 TeV, UPC NN W >5.5 GeV 4 10 γ γ γ γ PbPb γ γ 3 → 10 γ γ (PbPb V IP, IR 2 10 σ d γ γ V 10 20 30 40 50 M (GeV) γ γ σ monopole ր for larger values of kinematic variables σ realistic γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 7 / 22

E > 5 G E V γγ SCATTERING Photon collisions: MESON2018 number of count Photonic billiards might be the newest 60 game! γγ FUSION IN HEAVY ION UPC www.eurekalert.org/pub_releases/ PbPb PbPb → γ γ 50 s =5.5 TeV, UPC 2016-05/thni-pcp051916.php NN EPA W >5.5 GeV, | |<2.5 η γ γ (1/GeV) γ 40 -1 L =1 nb γγ SCATTERING int E > 5 G E V 30 E < 5 G E V γ γ dN/dM E < 2 G E V C ONCLUSION 20 several events / GeV 10 0 5 10 15 20 25 M (GeV) γ γ σ (PbPb → PbPb γγ ) [nb] at LHC ( √ s NN = 5 . 5 TeV) and FCC ( √ s NN = 39 TeV) boxes VDM-Regge cuts F realistic F monopole F realistic F monopole W γγ > 5 GeV 306 349 31 36 W γγ > 5 GeV, p t ,γ > 2 GeV 159 182 7E-9 8E-9 L E γ > 3 GeV 16 692 18 400 17 18 E γ > 5 GeV 4 800 5 450 9 611 H E γ > 3 GeV, | y γ | < 2 . 5 183 210 8E-2 9E-2 E γ > 5 GeV, | y γ | < 2 . 5 54 61 4E-4 7E-4 C p t ,γ > 0 . 9 GeV, | y γ | < 0 . 7 (ALICE cuts) 107 p t ,γ > 5 . 5 GeV, | y γ | < 2 . 5 (CMS cuts) 10 F W γγ > 5 GeV 6 169 882 C E γ > 3 GeV 4 696 268 574 C γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 8 / 22

E > 5 G E V γγ SCATTERING MESON2018 AA → AA γγ - THEORETICAL PREDICTIONS VS . EXPERIMENT γγ FUSION IN HEAVY ION UPC ➳ ATLAS Collaboration (M. Aaboud et al.), Evidence for light-by-light scattering in heavy-ion collisions with the ATLAS EPA detector at the LHC, Nature Phys. 13 (2017) 852 γγ SCATTERING E > 5 G E V E < 5 G E V E < 2 G E V C ONCLUSION ✗ p t γ > 3 GeV ✗ | η γ | < 2 . 4 ✗ M γγ > 6 GeV ✗ p t γγ < 2 GeV ✗ Aco < 0 . 01 ✔ γγ → γγ - using our calculations ✔ background: ATLAS ⇒ σ = 70 ± 20(stat.) ± 17(syst.) nb ✔ γγ → e + e − from ours model ⇒ σ = 49 ± 10 nb ✔ gg → γγ ✔ γγ → q ¯ q PRL (2013)/(2016) ⇒ σ = 45 ± 9 nb ✔ 13 events were observed γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 9 / 22

E > 5 G E V γγ SCATTERING MESON2018 AA → AA γγ - THEORETICAL PREDICTIONS VS . EXPERIMENT γγ FUSION IN HEAVY ION UPC ➳ CMS Collaboration, Measurement of light-by-light scattering in ultraperipheral PbPb collisions at √ s NN = 5.02 TeV, EPA CMS-PAS-FSQ-16-012 γγ SCATTERING E > 5 G E V E < 5 G E V 16 20 E < 2 G E V 18 PbPb → PbPb γ γ 14 PbPb → PbPb γ γ s = 5.02 TeV, UPC NN C ONCLUSION 16 s = 5.02 TeV, UPC -1 L = 390 µ b NN int (1/2.5 GeV) 12 -1 L = 390 µ b CMS preliminary data int 14 ✗ E t γ > 2 GeV (1/0.8) CMS preliminary data 10 12 ✗ | η γ | < 2 . 4 10 8 γ dN/dy γ ✗ M γγ > 5 GeV γ 8 dN/dM 6 6 ✗ p t γγ < 1 GeV 4 4 ✗ Aco < 0 . 01 2 2 0 0 6 8 10 12 14 16 18 20 2 1 0 1 2 − − y M (GeV) γ γ γ CMS ⇒ σ = 122 ± 46(stat.) ± 29(syst.) nb from ours model ⇒ σ = 103 ± 0 . 034 nb γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 10 / 22

E > 5 G E V γγ SCATTERING M γγ < 5 G E V ⇒ π 0 π 0 B ACKGROUND MESON2018 γγ FUSION IN ➳ M. K-G, A. Szczurek, HEAVY ION UPC π + π − and π 0 π 0 pair production in A A EPA photon-photon and in ultraperipheral γ γ π 0 ultrarelativistic heavy ion collisions, γγ SCATTERING γ Phys. Rev. C87 (2013) 054908 E > 5 G E V γ E < 5 G E V ➫ W γγ ∈ ( 2 m π − 6 ) GeV E < 2 G E V γ π 0 γ ➫ total cross section & C ONCLUSION angular distributions A A ➫ simultaneously for γγ → π + π − & π 0 π 0 γγ → π 0 π 0 3 10 π 0 π + π 0 π + e g n a Crystal Ball 2 h 10 c x ρ ρ e π - Belle + ρ ) [nb] π − 10 π 0 π − π 0 0 π f 0 (600) 0 π + / 0 π f 0 (980) π → sum f 2 (1270) p 1 f 0 (1500) γ Q γ f ′ ( 2 (1525) C σ f 2 (1565) π D -1 f 0 (1710) 10 f 2 (1950) π − / 0 f 4 (2050) -2 10 0 1 2 3 4 5 6 W = M [GeV] γ γ π π γγ FUSION IN HEAVY ION UPC MESON2018 K RAKÓW , 7-12 J UNE 2018 11 / 22