Exclusive diffractive results from ATLAS, CMS, LHCb, TOTEM at the LHC

Transcription

1 Exclusive diffractive results from ATLAS, CMS, LHCb, TOTEM at the LHC 1 Christohe Royon University of Kansas, Lawrence, USA On behalf of the ATLAS, CMS, LHCb and TOTEM collaborations 47th International Symosium on Multiarticle Dynamics, ISMD 2017, Setember , Tlaxcala City, Mexico LHCb results on vector meson roduction ATLAS results (dimuon, dihoton) CMS and CMS/TOTEM (dimuon, WW, ion) and rosects

2 What do we call Exclusive Diffraction / γ exchange events? 2 γ γ Left diagram: Double Pomeron Exchange: some energy is lost in Pomeron remnanats Next three diagrams: Exclusive roduction: the full energy is used to roduce dijets, vector mesons, no energy loss Dijet roduction via gluon exchange, QCD rocess (KMR) Photon exchange Vector meson roduction Possibility to reconstruct the roerties of the object roduced exclusively (via hoton and gluon exchanges) from the tagged roton: system comletely constrained Central exclusive roduction is a otential channel for BSM hysics: sensitivity to high masses u to 1.8 TeV

3 Measurement of central exclusive roduction in LHCb 3 Measurement of exclusive roduction of J/Ψ vector meson as an examle: Sensitivity to gluon distribution in Pomeron Signal: Central system with raidity gas Background: Diffractive rocesses (omeron remnants not detected, outside detector accetance) Exerimental issue: Detection of raidity gas New detectors in Run II: HERSCHEL, High Raidity Shower Counters for LHCb that allow a better suression of diffractive rocesses (detection of Pomeron remnants)

4 HERSCHEL 4

5 Veto on forward tracks Event selection and results at 13 TeV Further cleanu by veto on HERSCHEL signal significance 5

6 LHCb results on exclusive J/Ψ and Ψ(2S) Uncertainties highly correlated between bins Preferred model: JMRT NLO (JHEP 11 (2013) 085) 6

7 LHCb results on exclusive J/Ψ and Ψ(2S) cross sections 7 Measure the cross section, get σ(w ) from HERA extract σ(w+) (and vice versa at 7 TeV) Kinematic range extended at 13 TeV A simle ower law does not lead to a good descrition

8 CMS results on exclusive ion roduction 8 Exclusive ion roduction in CMS Soft Pomeron exchange is dominant at low mass: Photon exchange contribution is much suressed Measurement can be erformed in secial runs at low luminosity: no ile u, high cross section Exerimental signature: only two oosite tracks from the same rimary vertex; no additional signal in calorimeter; T (π) > 0.2GeV; y(π) < 2 Background comuted directly using data and same sign events (ure background samle)

9 CMS results on exclusive ion roduction 9 Data comared to the redictions from DIME MC (DPE) and STARLIGHT MC (ρ contribution) Disagreement with theory esecially in normalization as exected: MC does not contain roton dissociation events (ArXiv: ) σ π + π = 26.5±0.3(stat)±5.0(syst)±1.1(lumi) µb

10 ATLAS/CMS results on exclusive W W roduction 10 Look for W W exclusive roduction Motivation: sensitive to γγw W quartic anomalous coulings that could be a sign of new hysics Quartic gauge anomalous W W γγ and ZZγγ coulings arametrised by a W 0, a Z 0, a W C, a Z C L 0 6 e2 8 L C 6 a W 0 Λ 2 F µνf µν W +α W α a W C e2 16 Λ F µαf µβ (W +α W 2 β +W α W β + ) e 2 a Z C 16cos 2 (θ W ) Λ 2F µαf µβ Z α Z β Anomalous arameters equal to 0 for SM e 2 a Z 0 16cos 2 (θ W ) Λ 2F µνf µν Z α Z α

11 One aside: what is ile u at LHC? 11 Due to high number of rotons in one acket, there can be more than one interaction when two ackets collide Tyically u to 50 ile u events in Run II (about now) Analyses at high luminosity because of lower roduction cross section (exclusive WW, γγ...): need to fight ile u!

12 ATLAS/CMS results on exclusive W W roduction 12 Exclusive WW are rare (SM cross section of the order of 96.7 fb 1 ) full luminosity needed and reject ile u background CMS: 2011 at 7 TeV: 5.05 fb 1 ; 2012 at 8 TeV: 19.7 fb 1 ; ATLAS: 20.2 fb 1 Exclusive selection: oosite sign eµ from common rimary vertex, no extra track from vertex, M eµ > 20 GeV to avoid low mass resonances, eµ T > 30 GeV to remove Drell Yan and γ ττ CMS: σ( WW µe) = fb at 7 TeV (SM 4.0 ± 0.7 fb) σ( WW µe) = fb at 8 TeV (SM: 6.2 ± 0.5 fb) after correction for roton dissociation, ATLAS σ = 6.9±2.2(stat)±1.4(syst) fb (SM: 4.4 ± 0.3 fb) Observed significance for 7 and 8 TeV combination: 3.4 σ (CMS), 3.0 σ (ATLAS)

13 ATLAS/CMS results on exclusive W W roduction Most stringent limits on γγw W quartic anomalous couling JHEP08 (2016) 119 (CMS), Phys. Rev. D94 (2016) (ATLAS) 13

14 What is AFP/CT-PPS? 14 g g g jet jet γ γ Tag and measure rotons at ±210 m: AFP (ATLAS Forward Proton), CT-PPS (CMS TOTEM - Precision Proton Sectrometer) All hoton-induced cross sections involving anomalous coulings comuted using the Forward Physics Monte Carlo (FPMC) Sensitivity to high mass central system, X, as determined using AFP/CT-PPS: Very owerful for exclusive states: kinematical constraints coming from AFP and CT-PPS roton measurements

15 What is CT-PPS? 15 Joint CMS and TOTEM roject: htts://cds.cern.ch/record/ LHC magnets bend scattered rotons out of the beam enveloe Detect scattered rotons a few mm from the beam on both sides of CMS: 2016, first data taking ( 15 fb 1 )

16 Exclusive µµ roduction in ATLAS and in CT-PPS Turn the LHC into a γγ collider: flux of quasi-real hotons under the Equivalent Photon Aroximation, dileton roduction dominated by hoton exchange rocesses ATLAS: raidity ga selection: Exclusivity selection in resence of ile u vertices (µ 13): Require 0 additional track within 1 mm of µ + µ vertex, the challenge being to control the dissociative background, somewhat irreducible ATLAS: Fight Drell-Yan and other backgrounds by comaring data and MC background around the Z mass CT-PPS: Tag one of the two rotons 16

17 ATLAS: Fit the acolanarity 17 Events / GeV < m µ + µ < 70 GeV Data ATLAS -1 s = 13 TeV, 3.2 fb - Exclusive γγ µ + µ (ost-fit) S-diss γγ µ + µ (ost-fit) D-diss γγ µ + µ + Z/γ* µ µ Data / MC µ + µ acolanarity µ + µ acolanarity Fiducial cross section for µ T > 6 GeV (12 < m µµ <30 GeV); µ T > 10 GeV (30 < m µµ <70 GeV) and corrected for detector inefficiency Cross section extracted using binned maximum likelihood fit of N excl, N s diss : σ excl.fid γγ µµ = 3.12±0.07(stat)±0.10(syst) b

18 ATLAS results on exclusive dimuon roduction Cross section binned in dimuon mass and in dimuon mass divided by center-of-mass energy (ATLAS, ArXiv ) Look for absortive effects: Insufficient suression in Suerchic 2 (Khoze, Harland-Lang, Ryskin) 18 dσ / dm µ + µ - [b/gev] ATLAS -1 s = 13 TeV, 3.2 fb Data Stat. uncertainty Stat. syst. uncertainty EPA + finite-size correction SuerChic2 Theory uncertainty / σ EPA σ meas ATLAS ATLAS s = 13 TeV, 12 < m µ < 70 GeV + µ - CMS s = 7 TeV, m µ + > 11.5 GeV µ - ATLAS s = 7 TeV, m µ + > 20 GeV µ - ATLAS s = 8 TeV, m µ + > 45 GeV µ - EPA + finite-size correction SuerChic2 Stat. uncertainty Stat. syst. uncertainty Theo. uncertainty Theo./ Data m µ [GeV] + µ [GeV] m µ + - µ <m µ + µ -> / s

19 Observation of semi-exclusive dimuon roduction in CT-PPS 19 Observation of semi-exclusive dimuon roduction in CT-PPS First time a near-beam detector oerates at a hadron collider at high luminosity (single tag events), Request only one roton tagged (< 1 event exected for double tagged events due to accetance) Main Background is Drell-Yan di-muon roduction with roton from ile-u event: Data-driven estimate based on samle of Drell-Yan Z events, count number of Z events with ξ(µµ) and ξ() within 2σ and use MC to extraolate from Z eak to signal region

20 Observed signal (CT-PPS) First measurement of semi-exclusive di-muon rocess with roton tag CT-PPS works as exected (validates alignment, otics determination...) 17 events are found with rotons in the CT-PPS accetance and 12 < 2σ matching Significance for observing 12 events for a background of 1.47 ± 0.06(stat) ± 0.52(syst): 4.3 σ 20

21 Summary of 12 candidates roerties Dimuon invariant mass vs raidity distributions in the range exected for single arm accetance No event at higher mass that would be in the accetance for double tagging Highest mass event: 341 GeV CMS-PAS-PPS

22 Additional hoton exchange rocesses: dihoton roduction 22 SM QCD roduction dominates at low m γγ, QED at high m γγ Imortant to consider W loos at high m γγ At high masses ( 750 GeV), the hoton induced rocesses are dominant Conclusion: Two hotons and two tagged rotons means hoton-induced rocess

23 Exclusive dihoton roduction in ATLAS 23 Look for exclusive dihoton roduction in heavy ion P bp b collisions Cross section enhanced by a factor Z 4 In 480 µb 1 of data at s = 5.02 TeV, 13 events observed for 2.6 ± 0.7 background events For hoton E T > 3 GeV, η < 2.4, M γγ >6 GeV, γγ T < 2 GeV: σ = 70±24(stat)±17(syst) nb in agreement with SM Nature Physics 13 (2017) 852

24 Search for quartic γγ anomalous coulings in AFP/CT-PPS 24 γ γ γ γ Search for γγγγ quartic anomalous coulings Coulings redicted by extra-dim, comosite Higgs models No background after cuts for 300 fb 1 Phenomenology studies in collaboration between E. Chaon, O. Keka, C. Royon, M. Saimert, G. von Gersdorff, S. Fichet: Phys. Rev. D81 (2010) ; Phys.Rev. D89 (2014) , JHEP 1502 (2015) 165; Phys. Rev. Lett. 116 (2016) no 23, and Phys. Rev. D93 (2016) no 7, Events Signal γγ + ile u Excl. background ζ = 10 GeV 1 s = 14 TeV -1 L = 300 fb µ = 50 Events ζ 1 Signal γγ + ile u Excl. background = GeV -4 s = 14 TeV -1 L = 300 fb µ = ζ = 10 GeV miss m /m γγ ζ = 10 GeV y 1 y γγ

25 Conclusion Many comlementary results concerning exclusive diffraction at the LHC from the different exeriments: either using the raidity ga technique or the roton tags LHCb: J/Ψ and Ψ(2S) roduction: referred model JMRT NLO CMS exclusive ion roduction: disagreement with theoretical exectations robably due to the fact that roton dissociation is not included in models Best limits on γγww anomalous coulings in CMS Exclusive di-muon roduction: Comlementary measurements between CMS-TOTEM and ATLAS (first observation of high-mass exclusive dimuon roduction) γγγγ coulings: Observation by ATLAS in heavy ion mode and rosects for AFP and CT-PPS, highest ossible sensitivities to γγγγ, γγw W, γγzz, γγγz anomalous coulings due to new resonances, extra-dim. or comosite Higgs... 25

26 Examle of ATLAS selection: 1 mm Vertex exclusivity, µ+ µ T < 1.5 GeV requirement 26