Probing anomalous quartic coulings at the Large Hadron Collider with roton tagging Cristian Baldenegro University of Kansas cbaldenegro@ku.edu Setember 4, 07 /
Central exclusive reactions rocesses Central exclusive reactions + X + can be studied by measuring X (X = γγ, l l, W + W, ZZ) in a general urose detector (e.g., CMS, ATLAS) and the scattered intact rotons with forward roton detectors located at 0 m w.r.t. main interaction vertex. These can be due to γ-p, P P and γ γ exchanges. The final state can be reconstructed in its totality. + The exclusive channel allows us to robe ure gauge interactions with unrecedented sensitivity, since σ SM Excl is tyically small for m X > 600 GeV. Measure the roton fractional momentum loss ξ = / with the forward roton detectors w/ nominal accetance 0.05 < ξ, < 0.5. Event selection criteria: Comute the diffractive mass m = ξ ξ s and raidity y = log(ξ /ξ ) and comare with m X and y X. Central exclusive rocesses yield y = y X, m = m X. /
CMS-TOTEM Precision Proton Sectrometer (CT-PPS) Figure : Forward detector stations at about 0 m w.r.t. IP5. (Figure not in scale) Joint roject between the CMS and TOTEM collaborations. (Combine central and forward information to study central exclusive roduction). Oerating since Summer 06. Intact rotons from X reactions are detected with tracking sensors hosted in roman ots. Tracking + information of the accelerator magnetic lattice to reconstruct intact rotons kinematics (e.g., fractional momentum loss ξ). Observation of the µ + µ in CT-PPS CMS-PAS-PPS-7-00. Standard candle measurement for central exclusive roduction in at the LHC nominal luminosity. ATLAS Forward Physics aims for a similar hysics rogramme for central exclusive roduction. Oerating with both arms since Summer 07. 3 /
Anomalous quartic gauge coulings at the LHC It has been discussed before the ossibility of studying BSM ure gauge interactions γγγγ, γγw + W, γγγz in the exclusive channel. If there exists a quartic gauge couling, due to SU() U() Y we would exect quartic coulings with other combinations of vector bosons. As a roof of rincile, we will discuss the rosects of anomalous γγγγ couling reach at the LHC in collisions via hoton-induced rocesses with leading intact rotons in the final state, i.e., γγ. [S. Fichet, G. von Gersdorff, B. Lenzi, C. Royon, M. Saimert, 0.007/JHEP0(05)] and the γγγz anomalous couling rosects in central exclusive roduction. [C. Baldenegro, S. Fichet, G. von Gersdorff, C. Royon, JHEP 706 (07)] Figure : VV = γγ, ZZ, W + W, Zγ. 4 /
Anomalous quartic couling γγγγ Effective Field Theory assumtion, Λ New Physics s γγ. Coulings can be related to arameters of BSM extension of choice (e.g., wared extra-dimensions, comosite Higgs, new articles). The γγγγ interaction is induced by two dimension 8 oerators, L 4γ = ζ F µν F µνf ρσ F ρσ + ζ F µνf νρ F ρλ F λµ () Amlitudes M λ λ λ 3 λ 4 induced by the EFT oerators are imlemented in the Forward Physics Monte Carlo. Exciting result from ATLAS on Light-by-light scattering at low masses m γγ in PbPb collisions. [Nature Physics 3, 85858 (07)] 5 /
Anomalous quartic couling γγγγ The unolarized differential cross section induced by the EFT Lagrangian reads, dσ γγ γγ dω = 6π s (s + t + st) [ ] 48ζ + 40ζ ζ + ζ Imosing unitarity on the S-wave from the EFT amlitudes, we find the bound () ζ, ζ < (0 0 )GeV 4 (3) The quoted sensitivities are several orders of magnitude lower than this bound; form factor is not necessary within the mass accetance (m γγ [300 GeV, TeV]) 6 /
New Physics contributions to γγγγ couling s-channel exchange Induced by exchange of a neutral resonance on the s-channel. The effective couling is, (ζ, ζ ) = (f γ φ m) (d,s, d,s ) (4) Where /f γ φ is the tree-level couling, m its mass. Loo of heavy charged can induce the ζ, ζ coulings (ζ, ζ ) = α emq 4 m 4 N( c,s, c,s ) (5) Where Q is the charge, m mass, N number of coies. 7 /
Background in the exclusive γγ channel Exclusive background q/l/w γγ overlaed with ileu interactions q/l/w q/l/w q/l/w Khoze-Martin-Ryskin-like γγ (Highly suressed at high mass due to Sudakov factor for central exclusive rocesses). Photon-induced γγ ( 0 fb after accetance cuts) q/l/w q/l/w q/l/w q/l/w γγ + rotons from secondary interactions (ile-u). Reducible by exloiting exclusivity cuts set by roton taggers ξ, measurement (i.e., comare ξ central and ξ forward ) 8 /
Exclusive background Integrated cross-section [fb] 0 0 0 0 QCD contribution (KMR) Total QED cross-section Quark and Leton loos contribution W loo contribution FPMC (QED) and ExHuME (KMR) generator 3 0 Exclusive γγ roduction γ > 0 GeV, > 0 GeV γ T, T, 4 0 0 30 40 50 60 70 80 0 0 Cut on the di-hoton mass [GeV] Cross-section for SM exclusive reactions in γγ as a function of the m γγ cut. QCD contribution is highly suressed at high invariant masses comared to QED one. W ± loos dominate at high m γγ robed in the CT-PPS/AFP accetance. 9 /
Event selection γγ Events / 40 GeV 5 0 Signal 4 γγ + ile u 0 - e + e,dijet + ile u 3 0 Excl. background DPE background 0 0 0-3 -4 ζ = 0 GeV s = 4 TeV - L = 300 fb µ = 50 - -4 ζ = 0 GeV 0 400 600 800 000 00 400 600 800 000 m γγ [GeV] 0.05 < ξ < 0.5 (Forward roton detector accetance). By requesting T,γ,lead ( T,γ,sublead ) > 00(00) GeV and m γγ > 600 GeV, ractically only the signal and the γγ+ile-u background remain. T ratio, and asking γγ system back-to-back in the final selection cut (Toology for central exclusive rocesses). 0 /
Forward roton detector ξ, measurement Events / 0.0 0 0 Signal γγ + ile u Excl. background - -4 ζ = 0 GeV s = 4 TeV - L = 300 fb µ = 50 Events / 0.05 0 0 Signal γγ + ile u Excl. background - -4 ζ = 0 GeV s = 4 TeV - L = 300 fb µ = 50 0-3 - ζ = 0 GeV 0. 0.4 0.6 0.8..4.6.8 miss m /m γγ 0-3 -4 ζ = 0 GeV 0.5 0 0.5 y γγ - y Figure : Left: Missing diroton mass m to m γγ ratio. Right: Raidity difference y y γγ. Signal in black. Exclusive rocesses eak on the m /m γγ and y y γγ distributions. (Reminder: m = ξ ξ s, y = log(ξ /ξ )) Widths for the signal are due to the smearing on ξ, due to detector effects (3% smearing). Missing roton mass ξ ξ s matches m γγ for the signal within 5% resolution. /
Event selection Event selection considers Ldt = 300 fb and µ = 50 interactions er bunch crossing and fixed couling value at s = 4 TeV. Background free measurement for the γγ final state. The selection yields signal efficiency of 80% in this channel after all selections. No need for time-of-flight measurement to reject ile-u background in this channel. Asking for exclusivity (four-momentum conservation) is enough. /
ζ, ζ reach at CT-PPS/AFP Sensitivities down to O(0 3 ) GeV 4 in ζ, ζ at 95 % CL for Ldt = 300 fb at 4 TeV. 3 /
Coulings reach at the LHC with the exclusive channel. 0 - S=, brane γ. 0-4 S= ζ [ GeV -4 ] 0 S=/ SIHD comosite γ. 0-4. 0 -. 0 -. 0-4 0. 0-4. 0 - ζ [GeV -4 ] 95% C.L., 3 σ and 5σ reach in the anomalous coulings ζ, ζ in red, grey and yellow resectively for 300 fb and µ = 50. Coulings for which 0 after selection cuts in white. 4 /
Anomalous quartic couling γγγz Effective Field Theory assumtion, Λ New Physics s Zγ. Coulings can be related to arameters of BSM extension. The EFT γγγz couling is induced by two dimension-8 oerators, With F µν = ɛµνρσ F ρσ. L γγγz = ζ Zγ F µν F µνf ρσ Z ρσ + ζ Zγ F µν FµνF ρσ Zρσ (6) Z Possibility to study Z decay in l l and jets in exclusive channel. BR(Z q q) enhances sensitivity on ζ, ζ considerably. 5 /
Distribution of signal and background Z γ Events/60 GeV 5 0 4 0 3 0 0 0 - -4 ζ = 0 GeV -3-4 ζ = 0 GeV Zγ+ile-u ± W γ+ile-u qqe+ile-u s = 3 TeV Ldt = 300 fb µ = 50-0 400 600 800 000 00 400 600 800 000 00 m Zγ [GeV] Imlemented signal in the Forward Physics Monte Carlo. Background is simulated with PYTHIA8. For 300 fb and µ = 50 ile-u interactions at s = 3 TeV. Protons within the nominal accetance 0.05 < ξ, < 0.5. T,γ ( T,jj ) > 50(00) GeV and m Zγ > 700 GeV. Dijet and hoton balanced in momentum (Similar T and back-to-back). 6 /
Forward roton detector ξ, measurement (Excl. jjγ) Events/0.04 4 0 3 0 0 0 - -4 ζ = 0 GeV -3-4 ζ = 0 GeV Zγ+ile-u ± W γ+ile-u qqe+ile-u s = 3 TeV - Ldt = 300 fb µ = 50 Events/0.04 3 0 0 0 - -4 ζ = 0 GeV -3-4 ζ = 0 GeV Zγ+ile-u ± W γ+ile-u qqe+ile-u s = 3 TeV - Ldt = 300 fb µ = 50 0 0 0 3 0 0. 0.4 0.6 0.8..4.6.8 m /m Zγ 0.5 0.5 0 0.5.5 y -y Zγ Figure : Left: Mass ratio m /m Zγ. Right: Raidity difference y y jjγ. Signal in black. Signal eaks on the m /m Zγ and y y Zγ distributions. Criteria for exclusive event selection. Width for the signal are due to smearing on ξ, of % and the large smearing on the reconstructed jets energy. About 3 4 background events remain after alying selection cuts. Still, better sensitivity than in l lγ channel due to the larger 7 /
ζ Zγ, ζ Zγ reach at CT-PPS/AFP Sensitivities down to.3 0 3 GeV 4 in ζ, ζ at 95 % CL. The branching ratio BR(Z γγγ) has been constrained by ATLAS [Eur. Phys. J. C 76(4)]. This translates to the bound, ζ + ζ ζ ζ <.3 0 9 GeV 4 (95%CL) (7) Our sensitivity at 300 fb rovides a stronger constraint on ζ, ζ by a factor of 0 3. 8 /
ζ- ζ sensitivity lane ζ [0 3 GeV 4 ]..0.8.6.4..0 0.8 0.6 0.4 0. Non-accesible 95% C.L. 3 σ 5 σ 0.0 0.0 0. 0.4 0.6 0.8.0..4.6.8.0. ζ [0 3 GeV 4 ] 95% C.L., 3 σ and 5σ reach to the anomalous coulings ζ, ζ for 300 fb, µ = 50. Coulings for which 0 after selection cuts in dark blue. (Including 0.05 < ξ, < 0.5). 9 /
Further removal of ile-u interactions Time-of-flight measurement necessary for studying other interesting final states, e.g., exclusive W + W, where we can t aly the same kinematic constraints due to the missing energy carried by ν. Not strictly necessary for measurable final states, but hels reduce even further the ile-u background. Direct relation between timing resolution and longitudinal two-roton vertex resolution: δz = c δt For instance, a δt = 30s yields δz 6 mm 0 /
Summary We addressed the discovery otential for the anomalous quartic gauge coulings via hoton-induced rocesses in collisions with leading intact rotons at the LHC. Great background rejection ileu events by imosing four-momentum conservation. The irreducible SM contribution in this channel has a very low cross-section at high masses, which increases our reach in the anomalous quartic gauge coulings. Interesting studies on the way: Reach on semi-letonic W + W in the exclusive channel, low-mass resonances signatures at high invariant masses accessible to CT-PPS/AFP, Z -flux off rotons which may allow to reach 4Z coulings... Stay tuned for results with the CMS-TOTEM Precision Proton Sectrometer (CT-PPS) and ATLAS Forward Physics (AFP)! /