S. Bolognesi (1) from CMS A. Di Simone (2) from ATLAS 1 Università di Torino ed INFN Torino 2 Università di Roma Tor Vergata ed INFN Roma 2 V workshop italiano sulla fisica p-p ad LHC Perugia, 30 Gennaio - 2 Febbraio, 2008 LHC

Higgs at TevatronHiggs at Tevatron Higgs in ItalyHiggs in Italy Low mass searchesLow mass searches –ttbb –H –H H VV channelsH VV channels –H ZZ(*) 4l –HWWl l –HWWl l MSSM HiggsMSSM Higgs Combined resultsCombined results Discussion Outline 2 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia

Tevatron pessimistic scenario 5.83 fb -1 (same performance of 2007) realistic scenario 6.75 fb -1 Projected Integrated Luminosity in Run II Integrated luminosity [fb -1 ] /0301/0402/0503/0602/0704/0704/0805/09 Collected >3 fb -1, expected 6 or 7 fb -1 by the end of 2009 With 1.9 fb -1 analysis close to exclude wide range M H 160 GeV Sensitivity lower than expected in low M H region analyzed data expected 2009 Exclusion Limit: Tevatron Run II Preliminary 3 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia

Higgs in Italy!! ttH ttbb H H HZZ HWW higgs MSSM and BSM old analysis from Pavia; Perugia, Napoli Roma not yet started SM Pavia, Pisa; Milano, Roma Torino, Bari, (e.o.i Bologna, Padova, Trieste) Padova, Roma, Milano (e.o.i Bologna, Trieste) Milano, Bologna, Perugia, Pisa Genova Milano SM Pisa, CMS ATLAS Roma1, Roma2, LNF Genova, Cosenza, Pavia Roma1 in the next future MSSM: Roma1, Milano LNF, Roma1 4 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia MSSM Pisa

Low-mass searches Low Higgs mass favoured by EW precision measurements Most difficult mass region: with m H <130 GeV the most promising decay channels are into photons and taus ( 50 and 100 fb) very high background rate (also from fakes) VBF production channel gives the best s/b ratio in MSSM the di-photon decay channel is suppressed analyses focus on di-tau final state at low mass BR(Hbb) 70% but it cannot be a low lumi discovery channel: associated production ttH ( × BR 0.3 pb) very complex final state, many systematics involved huge QCD background 5 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia E.Gabrielli, F.Maltoni, B.Mele, M.Moretti, F.Piccinini and R.Pittau, Higgs boson production in association with a photon in vector boson fusion at the LHC,' Nucl. Phys.781 (2007) 64 [arXiv:hep-ph/ ] NEW IDEA: VBF Higgs with Hbb + request of a high p T central photon pioneer parton level study shows s/b increases of more then one order of magnitude (destructive interference in central emission in QCD bbjj):

ttH ttbb (M H 120 GeV) Complex final state (2W,4b) combinatorial background good detector control (b-tag, jet reco/calib,…) full simulation control samples (align, jet calib) CMS: S/B <0.1 with 60 fb -1 (NO discovery channel) [ 3 without syst.] low trigger efficiency WWl l WWl jj 77%63/52% more sophisticated trigger needed b-tag performance at best for p T jet 80 GeV (while ttbb contains many low p T jets) jet reco/calib. performance still poor energy flow / jets with tracks needed (they would improve also b-tag) Big QCD background (ttjj, ttbb) dedicated study on background normalization and shape from data multivariate technique 6 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia WWjjjj 25% ATLAS preliminary (after likelihood analysis)

… but better jet resolution: ATLAS: S/B 2.3 with 30 fb -1 (only semilept., NO systematics included) slightly worse efficiencyVSfake leptons performance … … similar btag performance … M(tbjj) ATLAS CMS 7 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia m16 GeV if soft muons added to b-jet M(Hbb) ATLAS m jjb =174GeV m = 11.7 GeV m bb =98GeV m = 20.0 GeV

H (M H 130 GeV) Vertex reco is crucial for correct mass measurement CMS: vertex fitted from high-p T tracks resolution 5mm (low lumi) ATLAS: calorimeter transverse granularity 1.6cm vertex from other tracks can be added too 40 m CMS / 0 and /jet discrimination needed to suppress huge reducible background ( j 10 3, jj 10 6 ) using hadronic leakage and shower shapes, exploiting calorimeter granularity (total rejection of ~3000 for efficiency of 80%) ATLAS: isolation against jets CMS: 0 rejection with Neural Network with input variables related to shower shape + silicon preshover info in the EndCaps 8 Andrea Di Simone - ATLAS Roma V workshop italiano su LHC - Perugia exploited

H (2) Photon conversions are important, due to material balance in inner detectors ATLAS: ~30% s convert in the barrel CMS: 42% in the barrel, 59.5% in the endcap Trigger based on detections of high-energy isolated photons ATLAS: 2 20i, 60, 2d20i|| 60 CMS: efficiency (2 12i) is 89.2% at L1 and 87.4% at HLT. no veto on tracks high trigger also for di-electron events Associated production allows to improve s/b ratio. Both ATLAS and CMS are studying several channels Advanced analyses (NN, Likelihood, categories) allow to improve results with low statistics CMS NN -1 : ATLAS: 6.3 cut based CMS: 6.0 cut based,8.2 NN 9 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma 7.7 fb -1 signal × 10

H (M H 130 GeV) ATLAS performing studies on all final states (ll, lh, hh), while CMS focused in the recent past on lh decay channel. Both experiments are focusing on VBF production channel, since it allows to improve s/b ratio. Main background: irreducible Zjj (QCD), help by CJV irredicible Zjj (EW) help by mass reconstruction reducible: QCD multi jet, W+jet, Z/ +jet, tt Trigger: ATLAS:e25i and mu20i for lh or ll final states. More complex trigger schemas (tau+mu or tau+e) are also under study. Single tau trigger exposes to huge QCD background, so for hh final state tau+MET seems the most promising trigger choice single e || single mu || e+tau || mu+tau at L1 and HLT CMS: 10 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma

H (2) Forward jet tagging: identifying the quark- initiated jets from VBF: typically in opposite hemispheres and high-p T CMS: selects the two highest Pt jets and requests opposite sign ATLAS: like CMS or choose the highest p T one and couple it with the highest found in the opposite hemisphere ATLAS challenge is to make it robust against additional pileup/fake jets Significances at 30 fb -1 ATLAS: lh M H =130 GeV, Sign. 4.4 lh + ll M H =130 GeV Sign. 5.7 CMS: lh M H =135 GeV, Sign CMS Central jet veto: no additional hard jets 11 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma Central jet veto

HVV channels 12 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma For M H >130 GeV, HVV most promising channels: effectiveness of ZZ and WW channels follows closely the BR shape m H 150 high ZZ BR and low backgrounds m H 170 low ZZ BR while HWW turns on m H 200 strong enhancement of ZZ BR for m H > 2m Z (suppression of WW) m H > 350 lower signal xsec and BR (due to Htt) VBF VVVV interesting per se as a probe of EWSB mechanism: Higgs in s-channel mass peak no Higgs SM unitarity violation

H ZZ(*) 4l channels Interesting over a wide mass range, mainly for their very clean signature: most critical mass region is GeV, where one Z is off-shell, leading to low p T leptons Backgrounds: ZZ*/ * 4leptons: irreducible background, cross section ~ tens of fb the biggest one after analysis selection Zbb: reducible (lepton isolation and impact parameter), cross section ~hundreds of pb, rejection factor ~O(10 3 ) needed: tt: reducible, rejection factor ~O(10 5 ) needed Reduce PDF, luminosity and background uncertainties normalizing from sidebands or using ZZ 4l) / Z 2l) Lepton identification and reconstruction are crucial for selection efficiency and H mass reconstruction: lepton performance measured from Z 2l 13 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma (big uncertainty on ggZZ)

H ZZ(*) 4l (2) Trigger: inclusive single mu/e, double mu, double e, have good signal efficiency and bg rejection Main systematics come from lepton energy scale/resolution and lepton-id efficiency results from single Zll (e.g. tag and probe) crucial for systematics control ATLAS mu reco CMS e reco 14 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma CMS ATLAS Preliminary

HWWl l (M H GeV) to be carefully monitored: bkgr normalization from real data systematic effects on background shape and normalization No mass peak: alternative variable ll) extrapolation from control regions (ad hoc for tt and WW) ATLAS documented work mainly about: MC physics model description: dedicated MC for ggWW interference between single top (produced in association with b) and double top Ex: 5.3% uncertainty on WW normalization (theoretical systematic dominates) 12.2% uncertainty on tt normalization (theor. syst. and jet energy scale) (10% of qqWW after cuts and different shape) detailed background normalization procedure and evaluation of theoretical uncertainties: for signal and most backgr. but p T (WW) modeled by PS (no NLO available) 15 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia preliminary ATLAS

CMS more focused on: simulation of real detector and real data workflow (trigger, skimming) detector performance measurement from data: electron identification efficiency extrapolated from Zee (tag & probe) lepton fake rate measured from QCD multi-jets events to evaluate the W+jets impact from MCfrom data different p T, spectra (different jet flavour decomposition under study) MET systematics from W mass measurement 5% on resol, 2% on scale comparison of W and Z with one lepton removed H WW l l : experimental systematics (e,MET) 16 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia CMS

MSSM Higgs discovery potential Light neutral h (same analysis of SM): particularly effective VBF with h complemented by VBF/ggF with HVV in the small scenario (low H- coupling) Heavier neutral A/H: high tg :bbH with h (, low BR but clean) low tg : GGF with A Zh llbb A/H l + MET Charged H ± : m H <m t : tttHb with H ggtbH gbtH with H (lower BR but cleaner) Htb m H >m t : high background (QCD, tt, tt+(b)jets, W+(b)jets) also combinatorial At intermediate tg, sensitivity only to h also with 300 fb -1 difficult to disentangle MSSM and SM 17 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia

MSSM study for low lumi ATLAS: bbh bb with M h M Z Z/ *bb background ( 10 2 signal ) has same diagrams! (only slightly different angular distrib. because Z vector, h scalar) difficult to be removed bbZ bbee as control sample: good control sample to measure detector performance on signal: reco efficiency M( ) resolution b-tag performances detector response differences > e more fake combinations with from b different inner brehmsstralung N Z N Zee ( ) 18 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia ATLAS

Summary 19 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia

For m H >140 GeV, ~1 fb 1 might be sufficient For low mass higgs (< 140 GeV) situation more complex: ~ 5 fb -1 needed and several channels must be combined Combined results 20 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia 5 discovery Exclusion 95% confid. level CMS + ATLAS These are inverse fbs of well understood data!! detector systematics: jets, /, MET (e and from Zll) multiple jets background xsec: V+jets, VV+jets, tt Plot from: J.J.Blaising, A.De Roeck, J.Ellis, F.Gianotti, P.Janot, G.Rolandi and D.Schlatter "Potential LHC contributions to Europe's Future Strategy at the High Energy Frontier"

Further reading… CMS physics TDR ATLAS physics TDR CMS note 2006/119 (ttHttbb) CMS notes 2006/078, 2006/97, 2006/112 (H ) CMS note 2006/088 (H ) CMS note 2007/037 (HWW) CMS notes 2006/136, 2006/130, 2006/115, 2006/122 (H4l) ATLAS: "Prospect for a Higgs discovery in the channel HWWl l with no hard jets" Mellado, Quayle, Wu ATL-PHYS-PUB (Z /Zee) 21 Sara Bolognesi - CMS Torino V workshop italiano su LHC - Perugia

S. Bolognesi from CMS Discussion V workshop italiano sulla fisica p-p ad LHC Perugia, 30 Gennaio - 2 Febbraio, 2008 A. Di Simone from ATLAS LHC

Avoid fake discovery 1 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma If we have a deviation from the SM expectations, how we should react? necessary prerequisites good comprehension of the detector (commissioning and integration) control of the systematics from standard candles (ex. Z,W for leptons) measure background (normalization and shape) from data clever tools to cross-check: comparison between similar channels (ex. e and ) work with ratios (ex: 4 /2, 2 /2e) good comprehension of the MC tools (comparison between MCs, close dialogue with theoreticians) prepare the analysis to make it possible!!

Weak points H ZZ (CMS just starting, ATLAS done in the physics TDR) ATLAS missing points: analysis sometimes based still on fast simulation Pileup & Cavern background effects often included but need to be studied systematically Channels still to be addressed or just started qqH qqbb (VBF) CMS missing points: jet reco performance still too low (energy flow work on-going) SUSY analysis should be more focused on real detector and low lumi scenarios ttH tt Theoretical study with additional 2 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma DISEGNO qqbbg Experimental study: (also fake) from fragmentation are not an issue (CMS Bologna using Pythia QCD sample)

Normalisation to pp Z 2l SM single Z 2l production cross-sections measured with great precision in an experiment which will have L ~ 10 fb -1. Calculate from MC the ratio R = (ZZ)/ (Z) –Full cancellation of LHC luminosities uncertainties –Partial cancellation of PDFs and QCD-scales uncertainties –Partial cancellation of experimental uncertainties (extrapolated) = R (Z) exp Discussion about using a similar approach in ATLAS too 3 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma

Theoretical and experimental uncertainty estimations for evaluation of background from single Z 2e measurements Normalisation to pp Z 2l 4 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma

Work on-going CMS: usage of CSA07 samples with misalignment/miscalibration in 10 pb -1 (100 pb -1 ) scenarios ATLAS: study of lepton systematics from data in Z/W events (2007 Notes) to be extrapolated in the various Higgs channels results to be published in the near future (CSC Notes) develop strategy to measure from data: detector performances and systematics (standard candles as W and Z) backgrounds shape and normalization (tt,V+jets,VV+jets) Focus on real detector and LHC environment (PU) simulation several issues (systematics, trigger, bkg from data) are being addressed for all the channels in the latest analysis 5 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma

Beyond start-up Mass and width Ex. ATLAS: qqH qqlnln / qq : Test of EWSB mechanism through VBF Ex. CMS: qqVV qqVV 6 fermions possible to distinguish SM from purely CP odd/even H to VV coupling possible to increase the limit on anomalous coupling CP,spin through VBF Ex. ATLAS: qqH qqlnjj: Ex. CMS: H e ZZ estimated precision <0.3% up to 350 GeV (stat error only) with 30 fb -1 if Higgs found direct measurement with reasonable accuracy can be performed only above ~250 GeV (better than 10% for M H >300 GeV with 300 fb -1 ) Ex. CMS + ATLAS: HZZ 6 V workshop italiano su LHC - Perugia Andrea Di Simone - ATLAS Roma Coupling to EW bosons through VBF

S. Bolognesi from CMS Back-up slides V workshop italiano sulla fisica p-p ad LHC Perugia, 30 Gennaio - 2 Febbraio, 2008 A. Di Simone from ATLAS LHC

Tevatron back-up 1

back-up 2 Slide by F. Gianotti

CMS improvement of the reconstruction backgr. and syst. from data Analysis focusing on HZZ*4l HWW*l l HWW*jjl / l l in VBF H in VBF early discovery channels significance > 5(3) with 30 fb -1 H other channels (mainly associated production) can help EXCLUDING Higgs (e.g. WHWWW*Wl l ) ttHttbb measure Higgs properties (mass, width, xsec) already with 30 fb -1 !! correct statistical treatment of results but good comprehension of detector needed (jet, MET, in lept. and hadr. decay) very difficult analysis with still quite unpredictable background at least 60 fb -1 (many jets also with low p T (<30 GeV) bad reso/eff) channel studied M H H ZZ*4l H WW*l l H WW*jjl H H H WW*l l VBF fb GeV fb GeV fb GeV pb GeV fb GeV fb GeV back-up 3

H ZZ(*) 4l one on-shell Z very sensible for M(H) = 130 to 500 (except where WW open) 2e 2 : highest BR but lower reso/effic on electrons 4 : golden channel greater than 50% for M(H)>115 greater than 85% for M(H)>150 statistical observation involving a small number of events compatibility with SM expectation: early discovery: preserving the phase space for more involved characterization measuring xsec, M H, width (spin, CP …) three channels 4e: most difficult (important to recover low p T electrons) isolated lepton from primary vertex with high p T (trigger) usual cuts M(H)=130 GeV back-up 4

2e2 analysis backgrounds: ZZ(*)/ *, tt, Zbb (Zcc found to be negligible) likelihood approach to discriminate real / fake e +/- internal bremsstrahlung recovery: 40%-10% events with (p T >5 GeV) radiation from lepton (1/3 from ) recovered with R(,l) < 0.3 e + e - with highest likelihood selected ECAL-Tracker matching, shower shape reconstruction offline selection before after m H =140GeVm H =200GeV 10 fb -1 N sign 12 N back 2 N sign 36 N back fb -1 back-up 5

2e2 results Background normalized from sidebands B = B stat B theory B stat increases with m H from 2% (m H 120) to 30% (m H 600) because of events decreasing in sidebands w.r.t. signal window B theory from PDF, QCD scale, NLO ZZ xsec 0.5% - 4.5% m H 150 high BR and low backgrounds m H 170 low BR at the HWW turn on m H 200 strong enhancement of BR for m H > 2m Z m H 250 decreasing of signal while ZZ background remains high m H decreasing of ZZ background m H > 350 decreasing of signal xsec and BR (due to Htt) Luminosity VS m H (same shape of 4 and 4e) back-up 6

4 analysis Half of the events used to optimize cuts with GARCON* which allows to obtain smooth M(4 ) dependent cuts: three main critical cuts uncorrelated: other half of the events used to compute significance MC generated sample mh150 muon isolation p T of the second lowest p T muon M(4 ) window ( 2 where H + reso) Reconstructed M(4 ) after selection s channel Z * t channel * Genetic Algorithm for Rectangular Cuts OptimizatioN allows to check effectively a large set of cuts which, in a straightforward approach, would take an astronomical amount of time back-up 7

4 background systematics Ratio H 4 to Z2 ( 1 fb -1 ) Normalization from sidebands (lower systematics but bigger statistical error) deep when b biggest new process NNLO ggZZ (20±8)% LO xsec (different initial state so variations of QCD scale do not necessary give a feel for its relative importance) back-up 8

4 results complementary approaches check the consistency with expected properties: M(4 ) shape consistency with sign+back hypothesis xsec and variables not used in the analysis decrease a priori the open phase space: M H prior probability could be forced to be consistent with the fit to precision EW measurements problem of significance overestimatimation of a local discovery in searching for a localized new phenomenon in a wide phase space use the early data for a first hint and then discard them from analysis back-up 9

4e analysis After trigger and preselectionAfter full analysis selection N signal 17 N backg 4 30 fb -1 : Optimization of low p T e +/- reco cuts to reject fakes are separately optimized for different Bremsstr. e +/- classes back-up 10

4e: systematics & reults Use Ze + e - with one golden e +/-, second e +/- used to estimate uncertainties 1% uncertainty on reco, isolation and identif. efficiency 0.5% barrel (1% endcaps) uncertainty on energy scale (best resolution on the Jacobian peak: p T m Z /2, low | |) Tracker radiography measuring the amount of e +/- Bremsstralhung (2% material budget with 10 fb -1 ) back-up 11

HWW(*)l l [M(H)= ] No narrow peak good background shape control necessary (normalization from data) high S/B needed signal: all leptonic W decays ( pb with a peak at M H160 GeV) WW, WZ, ZZ ( 15 pb) tt, tWb ( 90 pb) backgrounds: Z Drell-Yan not considered but checked that after selection should be < 2% of the total background mass independent cuts (ggWW) back-up 12

l l analysis central jet veto (| | 20 GeV) ee, e, reconstruction and selection intermediate m(ll) little (ll) in the transverse plane no calibration (energy is not needed) discrimination between real and fake jets (PU, UE, FSR, ISR, detector noise) > 0.2 for jets with 15 < E T < 20 GeV high MET (> 50 GeV) back-up 13

l l results Similar promising analysis specifically in VBF channel: B (tt) 16% B (WW) 17% dominated by statistic dominated by jet energy scale B from data defining free signal region varying the analysis cuts (values for 5 fb -1 ) B (WZ) 20% dominated by the presence of tt also tWb, ggWW small fraction of B: normalization region difficult to find syst uncertainties from MC theoretical error dominates (20%, 30%) background normalized to signal free region (M(ll)>110) back-up 14

qqH with HWWl jj [M(H) = ] + BR 5.5 BR(l l ) xsec pb + you can reconstruct the Higgs mass - big amount of background strong cuts good knowledge of physics needed (measure backgrounds from data) : tt + jets ( 840 pb) multiple jets xsec will be precisely measured from data many systematics about jets will be understood and resolved from data Wtb ( 100 pb) VV + jets ( 100 pb) V + jets ( 700 pb) 30 fb -1 16% detector systematics Loose Extra Jet Veto Extra Jet Veto back-up 15

CMS qq + Hl jj : jets (1) Strong E T cuts needed Parton-jet matching efficiency Strong E T cuts affect efficiency: (jets with E T <30 GeV very difficult to calibrate) for keeping an acceptable resolution for eliminating fake jets (most of PU jets with E T <30 GeV) m H = 170 signal forward quarks signal quarks from W decay (efficiency normalized to 1 for jet E T threshold of 16 GeV) Efficiency of requiring at least 4 jets tt + jets W + 4 jets W + 3 jets signal (efficiency normalized to 1 for jet E T threshold of 20 GeV) m H = 170 back-up 16

tag jets misidentified with jets from FSR, ISR, PU, UE, detector noise … In the signal this increases the chance of misidentification central jets from W jets from W: M(Wjj) using parton-jet matching best possible resolution of 15 GeV !! other central jets (E T >20 GeV in 60% of events) often (20%) with higher E T than jets from W m H = 170 MC calibration from QCD jet samples Iterative cone algorithm ( R=0.6) Fast Simulation for some backgrounds CMS qq + Hl jj : jets (2) back-up 17

qqH with H lep + jet [M(H)< 150] forward jets with high rapidity gap (no color exchange) high p T lepton (e or ) MET: resolution 20% after correction -jet identification backgrounds: Wl + jets ttbl bl with one jet misidentified as -jet complex signal kinematics: MC calibration central jet veto applied (with cut on parameter) Z/ * + jets (irreducible), offline trigger on little ( R) isolated jet impurity 2.7% energy resolution 11.3% efficiency 30% (mainly due to p T, cuts and request of isolation) back-up 18

H results M( ) computed using collinear approximation of visible part of decay products and neutrinos M( ) overestimated 5 GeV because of over-corrected MET M( ) resolution of 9.1% number of events computed from data using the M( ) fit (envisaged to do it in a region unaffected from signal) error ( B ) only from the fit: Significance exceeds 3 at 30 fb -1 10k toy MC data distributions each sample refitted with free scale factors for the three independent fit uncertainty = spread of the number of background events in the 10k samples following the fit (with the number of events equiv. to 30 fb -1 ) relaxed cuts back-up 19

Inclusive H [M(H)= ] inclusive signal production but with very low BR0.002 pp (irreducible) pp jets / + jets (reducible) with one jet misidentified as Drell-Yan e + e - very big background and very detector dependent + not well known QCD physics (big k factor in +jets events) Analysis based on NN trained on sidebands for backgr. on MC for signal (1% systematic error on the background interpolation under the Higgs peak) Great deal of uncertainty in the benchmark estimate of luminosity … … this will not be a systematic error on real data since the background will be measured from data (thanks to the big sidebands signal free) back-up 20