Standard Model at LHC: what we would like to learn form the first runs ( )

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1 MCWS, LNF, 28 February 2006 Standard Model at LHC: what we would like to learn form the first runs ( ) Barbara Mele Sezione di Roma

2 benefitted from talks on a similar subject by : A. De Roeck, G. Dissertori, F. Gianotti, D. Green, M. Mangano, P. Nason, G. Rolandi 2

2808x2808, N=3-5x10 10 partial to near full squeeze L=7x10 32-2x10 33 Stage 4 25 ns operation Push to nominal per bunch partial to full

3 current LHC schedule (up to ~15 pb -1 ) (up to ~1 fb -1 ) Stage 1 Initial commissioning 43x43 to 156x156, N=3x10 10 Zero to partial squeeze L=3x x10 31 Stage 2 75 ns operation 936x936, N=3-4x10 10 partial squeeze L= x10 32 Stage 3 25 ns operation 2808x2808, N=3-5x10 10 partial to near full squeeze L=7x x10 33 Stage 4 25 ns operation Push to nominal per bunch partial to full squeeze L=10 34 nominal luminosity : 2808 bunches (25 ns spacing), N=1.15 x / bunch, full squeeze at I.P. ( L ~ cm -2 s -1 )

4 1.00E E E E E E E E E Introduction Status of Machine Detectors Startup of Machine Detectors. First Physics 5 Events produced Pilot Run (lumi ~ cm -2 s -1 ) Minimum bias Jet Et>60 GeV Gamma + Jet P0>20 GeV 17 days 19 Barbara Mele Comments 1.00E+03 MCWS, LNF, 28/2/ Jet Et>25 GeV Jet Et>140 Gev W l nu Z ll ttbar--> l nu +X Pilot run is max 30 days (up to~15 pb -1 ) mainly for machine and detector commissioning! ECAL&HCAL calibration Tracker&Muon alignment efficient trigger operation data taking will be only for a small fraction of the time Pilot Run : Number of events Courtesy G. Rolandi 1.00E E E E E+05 Events produced Pilot Run A few million di-jet events with ET > 15 GeV within few hours! assumed efficiencies : Assumed efficienc!(jets) = 100%!(W) = 20%!(Z) = 20%!(ttbar) = 1.5%

5 Early Minimum-Bias Measurements E.g. charged particle density The pile-up for the future Energy dependence of dn/dη? Vital for tuning Underlying Event model Only requires a few thousand events. PYTHIA models favour ln 2 (s); PHOJET suggests a ln(s) dependence. Expected average pt=0.7 GeV 5

6 The Underlying Event (UE) No real theory : Hard Scattering need exp input! proton underlying event outgoing parton outgoing parton final-state radiation proton underlying event initial-state radiation Being studied in great detail at the Tevatron! Evidence that UE is the result of multiple semi-hard (mini-jet) interactions - modeling (learn from min. bias) - tune MCs (eg. Pythia) asap - how to subtract/merge it from/to hard scattering process??? 6

7 First Physics run in 2008! Run E fb E E E+01 cf. Tevatron : ~ 1 fb -1 today! 1.00E E-01 luminosity (10**30 cm-2 sec-1) events/crossing 100 pb -1 weeks integrated luminosity (pb-1) 7

8 SM expectations : 10% trigger bandwidth what will we do with that? will we just check again the Tevatron data??? 8

9 ) 2 ) 2 Events / 5 (GeV/c Events / 5 (GeV/c CDF CDF M ee and E/ T M ee and E/ T -1 CDF Run II Preliminary (200 pb ) CDF Run II Preliminary (200 pb ) 10 4 Data Data Drell - Yan 10 3 Drell - Yan 10 3 QCD Background!!, WW, WZ, tt QCD Background 10 2!!, WW, WZ, tt Dielectron Mass (GeV/c 2 ) dn/de/ T 10 2 dn/de/ T CDF preliminary CDF preliminary data (L=87 pb -1 ) Z+jets 10 2 data (L=87 pb -1 ) W+jets Z+jets tt+ww+wz+zz W+jets 10 tt+ww+wz+zz E/ T (GeV) LHC first 2 (crucial) steps: E/ T (GeV) Dielectron Mass (GeV/c ) Re-discover the Standard Model. Z/γ, W ± Drell-Yan rate and spectrum; jet inclusive to p j T GeV; near top cross thresholds sections; of W W, W Z, ZZ, W γ, γ+jets. b cross sections ; 9

10 LHC explores same final states as Tevatron but in a widely different partonic regime!!! x 1 x 2 = M2 S at fixed final state ( fixed M ) x 1 x 2 (LHC) 1 50 x 1x 2 (Tevatron) In a sense, we are studying the same final state in different QCD environments! Surprises? 10

11 LHC explores same final states but in a widely different partonic regime!!! x 1 x 2 = M2 S at fixed final state ( fixed M ) M(t t) x 1 x (LHC) x (Tevatron) 1x 2 In a sense, we are studying the same final state in different QCD environments! Surprises? M(Z)... of course, we ll also look at Q >> M(t t) 11

12 very hard processes ; σ(p T > p cut T ) [nb] Heavy fl (Herwig) jets check quark structure! Δσ(NLO) 10% Δσ PDF 5 100% 10 ev / fb -1 jet definition? jet reconstruction? t b 10 ev / fb -1 copious sources of high p t leptons B c s w Jet physics is complicated by theoreti b and t are copious sources of high p t le strong cross section, large branching. 10 ev / fb -1 Z l + l - may help for jet definition γ Important point: lepton may spectrum help for can b jet definition; My guess: it can also be measured relia th problems with γ isolation? jet energy calibration! 10 ev / fb -1 12

13 single high-pt leptons from : How come Q and W spectra are comparable at large Et? W e/µ+ ν The LO processes for QQ production are weighted by the gg or qqbar luminsity, which drops at large mass much more b e/µ+ X t rapidly Wb than L(qg) e/µ+ ν + b (at large pt, W and heavy quark production~ equal!) top, b lumi(m) b lepton spectrum can be predicted reliably! top W ALPGEN W M pt(lepton) [GeV] 13 23

14 Di-Jet : high rate, jet calibration (pt j balance), physics interest at large mjj 1 decade in lumi extends tail by 1 TeV! 1 (lumi for 10 events with M > Mjj) 14

Di-Jet resonances? σqcd (mjj ~950-1050 GeV) = 26 pb Exited quark 200 pb σqcd (mjj ~1.9-2.1 TeV) = 3.

15 Di-Jet resonances? σqcd (mjj ~ GeV) = 26 pb Exited quark 200 pb σqcd (mjj ~ TeV) = 3.5 pb Exited quark 8 pb CDF/D0 bounds at mjj < 1TeV LHC (10 pb -1 ) could extend searches! energy resolution crucial! (narrow resonances) 15

16 Produzione top Produzione del delttbar top ad ad LHC: LHC: plenty of Tops ttbar produced! ttbar ttbar Top production and bgs!!"#$$%&'()*!!"#$$%&'()*!!"#$$%&'()*!!"#$$%&'()* ++"#$$%&',)* ++"#$$%&',)* ++"#$$%&',)* (... at LHC) ++"#$$%&',)* 6&F* AA &&0&DE734&5(&6&7* 89:;<&! 0&DE734&5(&6&7* &0&DE734&5(&6&7* 89:;<&6&F* $$& 89:;<& 6&F* -./ &-./ 6&=* A -./ &0&12)34&5(&6&7* 89:;<& &0&12)34&5(&6&7* 89:;<&6&=* >?@&A Andrea Dotti, Leonado Andrea Dotti, LeonadoBenucci Benucci Andrea Dotti, Leonado Benucci!$$& 0&12)34&5(&6&7*89:;<&6&=*>?@&A &! -./!! Principalmente da gluon fusion Principalmente da gluon fusion! 6&=*>?@& A da gluon fusion $$&Principalmente &0&12)34&5(&6&7* 89:;<& ( 1 fb-1 collected on tape) -1ttbar 8 milioni di eventi all anno (rate di 1Hz) a 8 milioni di eventi ttbar all anno (rate di 1Hz) a 1 fb at LHC ~ 100 x Tevatron today 8 milioni di eventi ttbar all anno (rate di 1Hz) a Principalmente da gluon fusion bassa bassaluminosità luminosità bassa luminosità!!!!!(w+bbx)!(w+bbjj X) Also 8 milioni eventi ttbar all anno (rate di!(tt) [pb]di!(w+x) [ptb>20 GeV] [ptb,ptj >20 GeV] signal/bckgd Tevatron 6 20 x bassa luminosità improves! LHC x IIIIIIWorkshop WorkshopItaliano Italianosulla sullafisica FisicadidiATLAS ATLASe ecms CMS 3 e CMS III WorkshopBari, Italiano sulla Fisica di ATLAS Bari, Ottobre Ottobre Bari, Ottobre Increase Barbara Mele x 100 x 10 x 10 MCWS, LNF, 28/2/2006 x

wn statistics cross section atis LHC, notpair a Top : scale uncert. ~ 1%! simple selection : Missing ET, 1 lepton, events!4 jets, NO b-tag (!), cut on hadronic W -1 mass!

300 pb Atlas FullSim Preliminary No b-tagging required Anastasiou, Dixon, Melnikov, Petriello Missing ET > 20 GeV Segnale più fondo 1 lepton P > 20 GeV No b-tagging required T 4 jets(r=0.

17 wn statistics cross section atis LHC, notpair a Top : scale uncert. ~ 1%! simple selection : Missing ET, 1 lepton, events!4 jets, NO b-tag (!), cut on hadronic W -1 mass! limit for m(top) measurementsin!300 pb Atlas FullSim Preliminary No b-tagging required Anastasiou, Dixon, Melnikov, Petriello Missing ET > 20 GeV Segnale più fondo 1 lepton P > 20 GeV No b-tagging required T 4 jets(r=0.4) PT > 40 GeV Top pair events in 300 pb-1 bile migliorare S/B richiedendo solo gli on m(jj)-m(w) <10 GeV controls W+jets bckg!"#$%&'()!!"#$%&'() Mreco Study the top quark-./001%2 properties 34!",&'() mass, charge, spin, couplings, production and decay,!mtop ~ 1 GeV? Mreco important background for searches! Study the top quark properties 3 jets with highest pt! Jet energy scale from W"jet jet, e over the background, even without b tagging mass, charge, spin, couplings, production a y for W+/W- (ratios are good!!) decay,!mtop ~ 1 GeV? commission b-tagging ale uncertainty % 36!!"#$%$*'++ %$&'() a Fisica di ATLAS e CMS Ottobre %! LNF, important background for searches Barbara Mele MCWS, 28/2/ The signal is clearly visible over the background, even without b tagging

18 potential for new physics with 1 fb -1? events Heavy quark pairs Tevatron 15 pb -1 1 squark production beyond Tevatron reach even with 10 pb -1...! m(q) GeV 18

19 Di-lepton resonances May be seen very early: first weeks! 19

20 2008-run duty schedule vs integrated lumi after first good 10 pb W lν Z ll t t lν + jets measure rates, align and calibrate detectors better after first good 100 pb -1 W(Z)+jets rates well measurable Jet calibration, MET calibration (for SUSY) inclusive leptons, di-leptons, photons, di-photons triggers (for Higgs) from 100 pb -1 to 1 fb -1 Standard Model candles: tt production, W/Z cross sections, PDF studies, QCD studies, b-jet production do extensive MC tuning early Higgs boson search H γγ,ww,zz early SUSY-BSM searches MET + anything, di-jet, di-leptons, di-photons, resonances... 20

21 New Physics potential for 2008 run : Higgs?? L [10 30 cm -2 s -1 ] Re-discovery of the TOP SUSY - SUSY Z into muons 1.9 fb -1 + Di-jet resonanses + Heavy quarks + quark substructure +??? 100 pb -1! LHC = 30% 21

22 Conclusions We could have a very reach physics input within one year from the first bunch crossing... 22

23 and that s just the start up... γγ SHUTDOWN F. Moortgat, A. De Roeck 23

First physics with the ATLAS and CMS experiments. Niels van Eldik on behalf of the ATLAS and CMS collaborations

First physics with the ATLAS and CMS experiments Niels van Eldik on behalf of the ATLAS and CMS collaborations Content Status of the LHC and the ATLAS and CMS experiments Event production rates First physics