B EYOND 'S TANDARD 'M ODEL ' AT 'LHC - PowerPoint PPT Presentation

B EYOND 'S TANDARD 'M ODEL ' AT 'LHC XXVI'Seminario'Nazionale'di'Fisica'Nucleare'e'Subnucleare'“Francesco'Romano” 
 Otranto,'9G10'Giugno'2014' Lecture'2:'Exofca Shahram'Rahatlou 
 hQp://www.roma1.infn.it/people/rahatlou/

D IRECT 'S EARCHES ' AT 'LHC -31 10 ] 2 -Nucleon Cross Section [cm CMS MonoJet CMS CMS MonoPhoton -33 s = 7 TeV 10 CDF 2012 ∫ -1 L dt = 5.0 fb XENON-100 -35 10 CoGeNT 2011 CDMSII 2011 -37 10 CDMSII 2010 -39 10 -41 10 -43 10 χ a) Spin Independent -45 10 -1 2 3 10 1 10 10 10 2 M [GeV/c ] χ -1 CMS 4.9 fb s = 7 TeV 8 10 Neutralino Proper Decay Length [mm] -1 This experiment (4.9 fb ) 7 10 expected observed 6 10 -1 CDF with γ γ + E + Jets (2.6 fb ) 5 T 10 D0 with prompt + E (6.3 fb -1 ) γ γ T ATLAS with prompt + E (4.8 fb -1 ) γ γ 10 4 T 3 10 SPS8 2 10 ~ ∼ 0 GMSB χ → γ G 1 M = 2 Λ , tan( β )=15 m 10 N = 1, µ > 0 m 1 100 150 200 250 300 Neutralino Mass [GeV] Almost 200 papers on searches at LHC so far 104

EXO'S UMMARY ' IN 'ATLAS Shahram Rahatlou, Roma Sapienza & INFN 105

CMS'E XOTICA 'S UMMARY LQ1(ej) x2 LQ1(ej)+LQ1( ν j) LQ2( μ j) x2 Leptoquarks LQ2( μ j)+LQ2( ν j) LQ3( ν b) x2 stopped gluino (cloud) LQ3( τ b) x2 stopped stop (cloud) Long-Lived LQ3( τ t) x2 HSCP gluino (cloud) 0 1 2 3 4 HSCP stop (cloud) Particles q=2/3e HSCP RS1( γγ ), k=0.1 q=3e HSCP RS1(ee,uu), k=0.1 neutralino, ctau=25cm, ECAL time RS1(jj), k=0.1 RS Gravitons 0 1 2 3 4 RS1(WW → 4j), k=0.1 RS1(ZZ → 4j), k=0.1 j+MET, SI DM=100 GeV, Λ bulk RS(ZZ → lljj), k=0.5 j+MET, SD DM=100 GeV, Λ γ +MET, SI DM=100 GeV, Λ 0 1 2 3 4 Dark Matter γ +MET, SD DM=100 GeV, Λ l+MET, ξ =+1, SI DM=100 GeV, Λ Heavy Gauge l+MET, ξ =+1, SD DM=100 GeV, Λ SSM Z'( ττ ) Bosons l+MET, ξ =-1, SI DM=100 GeV, Λ SSM Z'(jj) l+MET, ξ =-1, SD DM=100 GeV, Λ SSM Z'(bb) 0 1 2 3 4 SSM Z'(ee)+Z'(µµ) Compositeness SSM W'(jj) SSM W'(lv) SSM W'(WZ → lvll) dijets, Λ + LL/RR SSM W'(WZ → 4j) dijets, Λ - LL/RR dimuons, Λ + LLIM 0 1 2 3 4 dimuons, Λ - LLIM Excited single e, Λ HnCM single μ , Λ HnCM Fermions e* (M= Λ ) inclusive jets, Λ + μ * (M= Λ ) inclusive jets, Λ - q* (qg) 0 3 6 9 12 15 q* (q γ ) b* ADD ( γγ ), nED=4, MS 0 1 2 3 4 ADD (ee, μμ ), nED=4, MS ADD (j+MET), nED=4, MD coloron(jj) x2 Multijet Large Extra ADD ( γ +MET), nED=4, MD coloron(4j) x2 gluino(3j) x2 QBH, nED=4, MD=4 TeV Resonances Dimensions gluino(jjb) x2 NR BH, nED=4, MD=4 TeV Jet Extinction Scale 0 1 2 3 4 String Scale (jj) Shahram Rahatlou, Roma Sapienza & INFN 95% CL E XCLUSION L IMITS (T E V) 0 3 6 9 12 15

R ESONANCES di-lepton mass Z � Z � ,G 1 , γ 1 Extended Gauge Symm Kaluza-Klein Excitations Graviton Randall-Sundrum di-photon mass • Resonances have a good record of past Nobel-worth discoveries! ! – charm and beauty Shahram Rahatlou, Roma Sapienza & INFN 107

E XTENDED 'G AUGE 'S YMMETRIES • New gauge bosons predicted by many extensions of the Standard Model with extended gauge symmetries ! – ZSSM in Sequential Standard Model with same Z0 coupling 
 as in Standard Model ! – Z’ ψ , Z’ χ , Z’ η models from E6 and SO(10) GUT groups ! – Left-Right symmetry model (LRM) and Alternative LRM (ALRM) ! – The Kaluza-Klein model (KK) from Extra Dimension ! – Little, Littlest Higgs model ! • No precise prediction for mass scale of gauge bosons ! • Discrimination of different models requires measurement of ! – cross section: limits with very little data ! – mass: exact value requires a visible peak ! – width: about same amount of data as for for mass ! – backward-forward asymmetry: requires high statistics in order to divide events in categories ! • Backgrounds ! – relatively clean with good S/B ! – mostly tails of SM processes ! • Experimental challenges ! – detector resolution can be a key player ! – 1.3% - 2.4% for electrons and 7% for muons at 1 TeV mass ! • extra care for energy/momentum reconstruction above 1 TeV Shahram Rahatlou, Roma Sapienza & INFN 108

E XTRA 'D IMENSIONS • Hierarchy problem: M EW /M Pl ~ 10 − 17 ! • Gravity much weaker than other gauge fields ! • Possible solution: Existence of extra dimensions! ! • Gravity scale lowered to ~ 1 TeV if gravitons propagate in 4+n dimensions ! – weak in our 4D universe but strongly interacting 
 in the extra dimensions ! • If ED similar to our 3+1 dimensions 
 Newton’s law affected ! – experimentally probed down to R < 160 microns ! • Tighter constraints if ED probed by elementary 
 particles ! – M = 100 GeV corresponds to distance of 10 -18 m ! • Several models available with possible 
 signatures to be seen at LHC ! – Graviton (and its KK modes), Black Holes Shahram Rahatlou, Roma Sapienza & INFN 109

O RIGIN ' OF 'E XTRA 'D IMENSIONS • The idea that space has extra, hitherto unobservable dimensions goes back to the beginning of the twentieth century, by Kaluza (1925) and Klein (1926). • It comes naturally in string theory. How come they are not visible today? (A) Because they compact and su ffi ciently small. (B) Because we are “stuck” on the 4D world. (C) Because they are of a more bizarre kind (for example, they are discretized appropri- ately) Shahram Rahatlou, Roma Sapienza & INFN 110

S MALL 'C OMPACT 'D IMENSION A compact, su ffi ciently small extra dimension is not visible ! A simple example of a space with one compact (circle) and one non- compact (real line) dimension: a hose of infinite length and radius R . There are two regimes: (A) At distance R the space looks like an (infinite) two-dimensional << plane. Shahram Rahatlou, Roma Sapienza & INFN 111

(B) At distance R the compact direction of the hose is invisible. >> The hose looks one-dimensional. R R 0 We will now make this intuition more precise. Shahram Rahatlou, Roma Sapienza & INFN 112

W ARPED 'E XTRA 'D IMENSION • Randall-Sundrum scenario ! – One warped Extra dimension ! ‣ 3D distances shrink between SM and Planck branes ! ‣ Boundary conditions in ED give rise to periodical wave functions 
 corresponding to well separated Graviton resonances 
 (aka Kaluza-Klein towers) ! ds 2 = e − 2 ky η µ ν dx µ dx ν + dy 2 ‣ parameters of metric determine mass of new particles ! ! • Gravitons propagate in bulk ! pp → G n → ll Gravity Scale: Λ π = M pl exp( � kr c π ) < 10 TeV ! Graviton Coupling c: 0.01 < c=k/M Pl < 0.1 c=1 Mass 1 st resonance: m 1 = kx 1 exp( � kr c π ) =3.83 Λ π c ! Width 1 st resonance: Γ 1 = ρ m 1 x 1 2 (k/M pl ) 2 c=0.5 c=0.1 ! • Production at hadron collider via coupling 
 c=0.05 Drell-Yan production of a 1.5 TeV G n and its to SM paticles 
 subsequent tower states c=0.01 q q , gg G e e , , , jets + − + − → → µ µ γγ KK Shahram Rahatlou, Roma Sapienza & INFN 113


 
 
 Z’'P RODUCTION ' AT 'LHC • Dominant Z’ production process via Drell-Yan process . ! u, d, s l ! q → Z 0 γ / Z / Z’ q ¯ ! • Clear experimental signature ! l u, d, s – 2 high pt leptons with large invariant mass ! – also decay in two jets but less sensitive than leptonic channels ! ‣ in some models ttbar dominates over leptons. pretty exotic! ! • Differential cross section 
 depends on ! – Z’ mass M= √ s’ ! negative charged lepton direction – Z’ rapidity Y ! – Angle θ * between l- and q in the center 
 θ * ! quark direction of mass of the colliding partons cos " * > 0 Shahram Rahatlou, Roma Sapienza & INFN 114

R ESONANCES • Comprehensive list of signatures ! – di-leptons ! RS1( γγ ), k=0.1 RS1(ee,uu), k=0.1 RS1(jj), k=0.1 ‣ e,mu,tau ! RS Gravitons RS1(WW → 4j), k=0.1 ‣ lepton+MET ! RS1(ZZ → 4j), k=0.1 bulk RS(ZZ → lljj), k=0.5 – di-bosons (W/Z) ! 0 1 2 3 4 ‣ 3l+MET ! Heavy Gauge ‣ 2l+2j ! SSM Z'( ττ ) Bosons SSM Z'(jj) – 2-photon ! SSM Z'(bb) SSM Z'(ee)+Z'(µµ) SSM W'(jj) • Backgrounds ! SSM W'(lv) SSM W'(WZ → lvll) – relatively clean with good S/B ! SSM W'(WZ → 4j) 0 1 2 3 4 – mostly tails of SM processes ! • Experimental challenges ! – detector resolution can be a key player ! – 1.3% - 2.4% for electrons and 7% for muons at 1 TeV mass ! – extra care for energy/momentum reconstruction above 1 TeV Shahram Rahatlou, Roma Sapienza & INFN 115

DI G ELECTRONS 7 10 Events Data 2012 ATLAS 6 Z/ * γ 10 Z’ ee → Top quark 5 ∫ -1 10 Dijet & W+Jets L dt = 20.3 fb Diboson s = 8 TeV 4 10 Z’ SSM (1.5 TeV) Z’ SSM (2.5 TeV) 3 10 2 10 10 1 -1 10 Data/Expected 1.4 1.2 1 0.8 0.6 0.08 0.1 0.2 0.3 0.4 0.5 1 2 3 4 m [TeV] ee • Background mainly composed of Drell-Yan tail Shahram Rahatlou, Roma Sapienza & INFN 116

D I GM UONS 7 10 Events Data 2012 ATLAS 6 10 Z/ γ * Z’ → µ µ Top quark 5 ∫ -1 10 L dt = 20.5 fb Diboson s = 8 TeV 4 Z’ SSM (1.5 TeV) 10 Z’ SSM (2.5 TeV) 3 10 2 10 10 1 -1 10 Data/Expected 1.4 1.2 1 0.8 0.6 0.08 0.1 0.2 0.3 0.4 0.5 1 2 3 4 m [TeV] µ µ • wider peak structure ! – momentum resolution of high pt muons worse than energy resolution for high energy electrons Shahram Rahatlou, Roma Sapienza & INFN 117

L OOKING ' FOR 'D EVIATIONS Shahram Rahatlou, Roma Sapienza & INFN 118