Other ATLAS Jet Measurements

Transcription

1 Other ALAS Jet Measurements Michael Begel Aril,

2 Jets as Hard Probes Michael Begel Standard LHC ALAS Jet Measurements Aril, High dijet roduction rovides a owerful robe of the hard scatter recision tests of QCD constraints on arton distribution functions sensitivity to the resence of new hysical henomena dijet resonances quark comositeness large extra dimensions

3 Jets as Hard Probes Michael Begel Standard LHC ALAS Jet Measurements Aril, 3 High dijets are also a key robe for understanding activity in the rest of the event... azimuthal angle between leading two jets radiation between two leading or two most forward jets... and within the jet jet shaes hese measurements test QCD calculations and constrain henomenological models.

4 Azimuthal Decorrelations Michael Begel Standard LHC ALAS Jet Measurements Aril, 4 φ between the leading two jets in an event reflects the activity in the rest of the event soft radiation causes small decorrelations hard radiation, such as from the resence of additional jets, can cause large decorrelations φ tests QCD calculations for multijet final states without requiring the measurement of additional jets ] - /σ dσ/d φ [radians ALAS Simulation s=7 ev jets R=.6 > GeV y < > GeV ALPGEN φ dijet Σ Partons 5 Partons 4 Partons 3 Partons Partons / /3 5/6 φ [radians]

5 Azimuthal Decorrelations Michael Begel Standard LHC ALAS Jet Measurements Aril, 5 Measure normalized dijet differential cross section: σ dσ d φ anti-k jets with R =.6 jet > GeV leading two jets y < accetance out to y <.8 cross section normalized searately for each bin Number of Events ALAS s=7 ev jets R=.6 > GeV y <.8 Leading two jets: y < > GeV - Data L dt=36 b jets 3 jets 4 jets 5 jets PYHIA 85 events have 5 jets with > GeV / /3 5/6 φ [radians] arxiv:.696 [he-ex] (acceted by PRL)

6 NLO QCD heory Comarison Michael Begel Standard LHC ALAS Jet Measurements Aril, 6 ] - σ dσ/d φ [radians / ALAS jets R=.6 - Data L dt=36 b 8 > 8 GeV ( ) 7 6< 8 GeV ( ) 6 5< 6 GeV ( ) 5 4< 5 GeV ( ) 4 3< 4 GeV ( ) 3 6< 3 GeV ( ) < 6 GeV ( ) 6< GeV ( ) < 6 GeV ( ) s=7 ev > GeV y < NLO QCD O(α s PDF & α s unc. scale unc. / /3 5/6 φ [radians] arxiv:.696 [he-ex] (acceted by PRL) 4 ) ratio to NLO QCD σ dσ/d φ / ALAS s=7 ev L dt=36 b - < 6 GeV 6< 3 GeV.5 5< 6 GeV / /3 5/6 NLO QCD 4 ) O(α s scale unc. unc. PDF & α s 6< GeV 3< 4 GeV 6< scale uncertainty large where NLO QCD dominated by real O(α 4 s) diagrams 8 GeV /3 5/6 jets R=.6 > GeV y < < 6 GeV 4< 5 GeV > 8 GeV /3 5/6 φ [radians] comarison excluded where NLO QCD diverges ( φ )

7 Event Generator Comarison Michael Begel Standard LHC ALAS Jet Measurements Aril, 7 ] - σ dσ/d φ [radians / ALAS jets R=.6 - Data L dt=36 b 8 > 8 GeV ( ) 7 6< 8 GeV ( ) 6 5< 6 GeV ( ) 5 4< 5 GeV ( ) 4 3< 4 GeV ( ) 3 6< 3 GeV ( ) < 6 GeV ( ) 6< GeV ( ) < 6 GeV ( ) s=7 ev > GeV y < SHERPA PYHIA HERWIG / /3 5/6 φ [radians] arxiv:.696 [he-ex] (acceted by PRL) ratio to SHERPA σ dσ/d φ / ALAS s=7 ev L dt=36 b - < 6 GeV 6< 3 GeV 5< 6 GeV / /3 5/6 PYHIA HERWIG SHERPA stat. unc. 6< GeV 3< 4 GeV 6< 8 GeV /3 5/6 jets R=.6 > GeV y < < 6 GeV 4< 5 GeV > 8 GeV /3 5/6 φ [radians]

8 Event Generator Comarison Michael Begel Standard LHC ALAS Jet Measurements Aril, 8 ratio to PYHIA AMB...5. ALAS s=7 ev L dt=36 b - < 6 GeV PYHIA8 4C PYHIA D6 PYHIA DW PYHIA MC9 6< GeV jets R=.6 > GeV y < < 6 GeV ratio to PYHIA AMB...5. ALAS s=7 ev L dt=36 b - < 6 GeV PYHIA AMB (k ISR =4.) PYHIA AMB (k ISR =.5) PYHIA AMB (k ISR =.) 6< GeV jets R=.6 > GeV y < < 6 GeV σ dσ/d φ /..5 6< 3 GeV 3< 4 GeV 4< 5 GeV σ dσ/d φ /..5 6< 3 GeV 3< 4 GeV 4< 5 GeV < 6 GeV / /3 5/6 6< 8 GeV /3 5/6 > 8 GeV /3 5/6 φ [radians].5 5< 6 GeV / /3 5/6 6< 8 GeV /3 5/6 > 8 GeV /3 5/6 φ [radians] arxiv:.696 [he-ex] (acceted by PRL)

9 Dijet Production with Jet Veto Michael Begel Standard LHC ALAS Jet Measurements Aril, 9 Measure the hard radiation in the raidity interval between two jets: sensitive to BFKL dynamics sensitive to wide-angle soft-gluon radiation color-singlet exchange his measurement also robes theory redictions and exerimental techniques relevant for VBF Higgs searches. φ y this is different than the traditional ra ga measurement focused solely on color-singlet exchange

10 Michael Begel Standard LHC ALAS Jet Measurements Aril, Boundary Conditions Event Selection: anti-k jets with R =.6 boundary jets require > GeV and y < 4.5 of boundary jets > 5 GeV veto jet > GeV single interaction-vertex events Selection A boundary jets have highest increased sensitivity to wide-angle soft-gluon radiation φ Selection B boundary jets have most forward y increased sensitivity to BFKL dynamics φ Observables (in and y): y Mean Jet Multilicity: between boundary jets Ga Fraction: fraction of events without jet in ga y

11 Jet Multilicity Number of jets in ga.6 Selection A Q = GeV < y < 3 Data Number of jets in ga PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Selection A Q = GeV 9 < < GeV MC/Data.4. MC/Data.4. ALAS Preliminary.6 ALAS Preliminary [GeV] φ y y ALAS-CONF--38 Michael Begel Standard LHC ALAS Jet Measurements Aril,

12 Jet Multilicity Michael Begel Standard LHC ALAS Jet Measurements Aril, Number jets in ga < y < 5 (+3.3) 3 < y < 4 (+.) < y < 3 (+.) < y < (+) ALAS Preliminary Data (+syst) HEJ (arton level) POWHEG + PYHIA Number jets in ga POWHEG + HERWIG Selection A Q = GeV < y < 5 (+3.3) 3 < y < 4 (+.) < y < 3 (+.) < y < (+) ALAS Preliminary Data (+syst) HEJ (arton level) POWHEG + PYHIA POWHEG + HERWIG Selection B Q = GeV φ φ y [GeV] [GeV] ALAS-CONF--38 y

13 Ga Fraction Ga fraction Ga fraction Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Selection B Q = GeV < y < Selection B Q = GeV 9 < < GeV MC/Data.4. ALAS Preliminary MC/Data.4. ALAS Preliminary [GeV] φ y y ALAS-CONF--38 Michael Begel Standard LHC ALAS Jet Measurements Aril, 3

14 Ga Fraction Michael Begel Standard LHC ALAS Jet Measurements Aril, 4 Ga Fraction < < 8 < 5 < < 9 < 7 < < 7 GeV (+3.6) < 4 GeV (+3) < GeV (+.4) < 8 GeV (+.8) < 5 GeV (+.) < GeV (+.6) < 9 GeV (+) Data (+syst) HEJ (arton level) POWHEG + PYHIA Ga Fraction POWHEG + HERWIG Selection A Q = GeV ALAS Preliminary < < 8 < 5 < < 9 < 7 < < 7 GeV (+3.6) < 4 GeV (+3) < GeV (+.4) < 8 GeV (+.8) < 5 GeV (+.) < GeV (+.6) < 9 GeV (+) Data (+syst) HEJ (arton level) POWHEG + PYHIA POWHEG + HERWIG Selection B Q = GeV ALAS Preliminary φ φ y y y ALAS-CONF--38 y

15 Jet Shaes Parton showers evolve until they hadronize at Q Λ QCD he shaes of high- jets are dictated more by multi-gluon emission than by the fragmentation rocess Measurements of jet shaes: are sensitive to the mixture of quark & gluon final states and to the running of α s test arton-shower models are also sensitive to the jet algorithm and to the underlying event gluons radiate more than quarks so gluon-initiated jets tend to be broader than quark-initiated jets Michael Begel Standard LHC ALAS Jet Measurements Aril, 5

16 Jet Shaes Michael Begel Standard LHC ALAS Jet Measurements Aril, 6 Event Selection: anti-k jets with R =.6 jet > 3 GeV and y <.8 single interaction-vertex events ρ(r) = r N jet jets (r r/, r + r/) (, R), r/ r R r/ ψ(r) = N jet jets (, r) (, R), r R

17 Differential Jet Shaes Michael Begel Standard LHC ALAS Jet Measurements Aril, 7 ρ (r) ALAS jets R =.6 3 GeV < < 4 GeV y <.8 ρ (r) DAA / MC -. - Data L dt =.7 nb - 3 b PYHIA-Perugia HERWIG++ ALPGEN PYHIA-MC r DAA / MC - ALAS jets R =.6 GeV < < 6 GeV y < r ρ (r) ρ (r) PRD 83, 53 () ALAS ALAS - jets R =.6 6 GeV < < 3 GeV y <.8 - jets R =.6 5 GeV < < 6 GeV y <.8 DAA / MC r DAA / MC r

18 Integrated Jet Shaes Michael Begel Standard LHC ALAS Jet Measurements Aril, 8 - Ψ(r =.3) jets R =.6 y <.3 - Ψ(r =.3) - - Data L dt =.7 nb - 3 b PYHIA-Perugia Perugia (di-jet) gluon-initiated jets Perugia (di-jet) quark-initiated jets jets R =.6. < y <.8 ALAS.5 ALAS (GeV) (GeV) PRD 83, 53 ()

19 Integrated Jet Shaes Michael Begel Standard LHC ALAS Jet Measurements Aril, 9 - Ψ(r =.3) Ψ(r =.3) PRD 83, 53 () ALAS jets R =.6 3 GeV < < 4 GeV....9 ALAS jets R =.6 6 GeV < < 8 GeV Ψ(r =.3) ALAS jets R =.6 6 GeV < < GeV y - Ψ(r =.3) jets R =.6 3 GeV < - Data L dt =.7 nb - 3 b PYHIA-Perugia HERWIG++ ALPGEN PYHIA-MC9 PYHIA-DW < 4 GeV - ALAS y y y

20 Jet Resonse Michael Begel Standard LHC ALAS Jet Measurements Aril, Quark- and gluon-initiated jets have different calorimetric resonse gluon-initiated jets tend to be broader, with more lower-momentum articles, than quark-initiated jets these effects are being incororated into the jet energy calibration true / reco Resonse= ALAS Preliminary Simulation PYHIA AMB Light-quark Jets Gluon Jets All Jets η < R=.6 Jets 3 [GeV] true true / reco Resonse= ALAS Preliminary Simulation PYHIA AMB Light-quark Jets Gluon Jets All Jets. η <.8 R=.6 Jets [GeV] ALAS-CONF--53 true

21 Fitting the Jet Resonse Michael Begel Standard LHC ALAS Jet Measurements Aril, Event Selection: anti-k jets with R =.6 (and also R =.4) jet > 6 GeV and y <.8 single interaction-vertex events Arbitrary Units ALAS Preliminary Simulation PYHIA AMB Light-quark Jets Gluon Jets reco 8 < GeV η <, Isolated Jets n trk Arbitrary Units ALAS Preliminary Simulation PYHIA AMB Light-quark Jets Gluon Jets reco 8 < GeV Width η <, Isolated Jets ALAS-CONF--53

22 Fitting the Jet Resonse Michael Begel Standard LHC ALAS Jet Measurements Aril, Arbitrary Units ALAS Preliminary - L dt=.43 b Data s=7 ev PYHIA AMB PYHIA Perugia HERWIG++ η <, Isolated Jets reco 8 < GeV n trk Arbitrary Units ALAS Preliminary - L dt=.43 b Width Data s=7 ev PYHIA AMB PYHIA Perugia HERWIG++ η <, Isolated Jets reco 8 < GeV Heavy-flavor fraction has been fixed to that of the event generator. ALAS-CONF--53

23 Fitting the Jet Resonse Michael Begel Standard LHC ALAS Jet Measurements Aril, 3 Fraction of Jets Uncertainty ALAS Preliminary - L dt=.43 b Gluon Jets Light Jets b/c Jets Data: Solid Points. Width emlate Fits Heavy flavor syst. JES syst. Shae syst. Model syst. ALP/PY syst. Combined 3 4 Inclusive Jet Multilicity Fraction of Jets Uncertainty ALAS Preliminary - L dt=.43 b Gluon Jets Light Jets b/c Jets Data: Solid Points. emlate Fits n trk Heavy flavor syst. JES syst. Shae syst. Model syst. ALP/PY syst. Combined 3 4 Inclusive Jet Multilicity Results fit to data are closed markers ( ) while results from simulation are oen markers ( ). Heavy-flavor fraction has been fixed to that of the event generator. ALAS-CONF--53

24 Summary Michael Begel Standard LHC ALAS Jet Measurements Aril, 4 Dijet Azimuthal Decorrelations reflects the activity in the rest of the event described by NLO QCD, ME+PS (SHERPA), and tuned event generators Jets located in the raidity intervals between boundary jets sensitive to BFKL dynamics and wide-angle soft-gluon radiation ga fraction and mean jet multilicity described by PYHIA and POWHEG+PYHIA HERWIG and ALPGEN+HERWIG redict too much activity between jets deendence not described by HEJ (not interfaced with PS) Jet Shaes narrow with increasing and y (quark/gluon mixture & running of α s ) described by PYHIA Perugia but less so by other tunes or event generators Jet Resonse systematic uncertainties associated with the jet energy calibration can be reduced by including jet-shae information hese results test imortant asects of QCD and will benefit global efforts to roduce henomenological tunes for the event generators.

25 Backu Michael Begel Standard LHC ALAS Jet Measurements Aril, 5

26 Event Dislay Michael Begel Standard LHC ALAS Jet Measurements Aril, 6 Jet :.3 ev (η =., φ =.8) Jet :. ev (η =., φ =.5) E = 4 GeV

27 Event Dislay Michael Begel Standard LHC ALAS Jet Measurements Aril, 7 Jet : 9 GeV (η =.9, φ =.7) Jet : GeV (η =.3, φ =.9) E = GeV E = 89 GeV

28 Jet Multilicity Number of jets in ga.6 Selection B Q = GeV < y < 3 Data Number of jets in ga PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Selection B Q = GeV 9 < < GeV MC/Data.4. MC/Data.4. ALAS Preliminary.6 ALAS Preliminary [GeV] φ y y ALAS-CONF--38 Michael Begel Standard LHC ALAS Jet Measurements Aril, 8

29 Jet Multilicity Michael Begel Standard LHC ALAS Jet Measurements Aril, 9 Number of jets in ga < < 8 < 5 < < 9 < 7 < < 7 GeV (+4.4) < 4 GeV (+) < GeV (+9.6) < 8 GeV (+7.) < 5 GeV (+4.8) < GeV (+.4) < 9 GeV (+) ALAS Preliminary Data (+syst) HEJ (arton level) POWHEG + PYHIA Number of jets in ga POWHEG + HERWIG Selection A Q = GeV < < 8 < 5 < < 9 < 7 < < 7 GeV (+4.4) < 4 GeV (+) < GeV (+9.6) < 8 GeV (+7.) < 5 GeV (+4.8) < GeV (+.4) < 9 GeV (+) ALAS Preliminary Data (+syst) HEJ (arton level) POWHEG + PYHIA POWHEG + HERWIG Selection B Q = GeV φ φ y y y ALAS-CONF--38 y

30 Ga Fraction Ga fraction Ga fraction Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Data PYHIA 6 AMB HERWIG++ ALPGEN + HERWIG/JIMMY Selection A Q = GeV < y < Selection A Q = GeV 9 < < GeV MC/Data.4. ALAS Preliminary MC/Data.4. ALAS Preliminary [GeV] φ y y ALAS-CONF--38 Michael Begel Standard LHC ALAS Jet Measurements Aril, 3

31 Ga Fraction Michael Begel Standard LHC ALAS Jet Measurements Aril, 3 Ga Fraction < y < 6, (+4) 4 < y < 5, (+3) 3 < y < 4, (+) < y < 3, (+) < y <, (+) Data (+syst) HEJ (arton level) POWHEG + PYHIA Ga Fraction POWHEG + HERWIG Selection A Q = GeV < y < 6, (+4) 4 < y < 5, (+3) 3 < y < 4, (+) < y < 3, (+) < y <, (+) Data (+syst) HEJ (arton level) POWHEG + PYHIA POWHEG + HERWIG Selection B Q = GeV φ φ ALAS Preliminary ALAS Preliminary y [GeV] [GeV] ALAS-CONF--38 y