Multi-differential jet cross sections in CMS

Transcription

1 Multi-differential jet cross sections in CMS A. Bermudez Martinez on behalf of the CMS collaboration. Deutsches Elektronen-Synchrotron (DESY) April 07 A. Bermudez (DESY) April 07 / 5

2 QCD Main background to almost any interesting and rare event at a hadron collider. Understood in terms of factorization theorems. Extraction of α s and PDFs. Many subtleties remain unclear (MM schemes, PS and resummation, factorization breaking and soft gluons color correlations...) Jets measurements Partons express themselves through collimated streams of hadrons. A. Bermudez (DESY) April 07 / 5

3 Double-differential inclusive jets cross sections in pp collisions at s = 8eV DOI:.07/JHEP03(07)56 Double-differential inclusive jet cross sections in pp collisions at s = 3eV DOI:.40/epjc/s A. Bermudez (DESY) April 07 3 / 5

4 Inclusive jets cross and 3eV d σ = dp dy ɛl int,eff N jets p ( y ) pb GeV σ dy d dp 7 4 CMS 8 ev - Open: L = 5.6 pb int - Filled: L int = 9.7 fb C NLO NP EWK C NLO NP - p + p jet + X probes parton-parton interaction (Benchmark QCD test) - Sensitive to α s - Provides important PDFs constraints - QCD describes data within 4 orders of magnitude!! - Experimental uncertainties dominated by JES, unfolding and the integrated luminosity. - Strongly p and y dependent PDF uncertainties (dominant) Inclusive jets cross - anti-k t7, bins of rapidity [0, 4.7] Inclusive jets cross - anti-k t4 and anti-k t7, bins of rapidity [0, 4.7] y < 0.5 ( ) < y <.0 ( ) 4.0 < y <.5 ( ) 3.5 < y <.0 ( ) 4.0 < y <.5 ( ).5 < y < 3.0 ( ) < y < 4.7 ( ) Jet p [GeV] Jet p (GeV) A. Bermudez (DESY) April 07 4 / 5 dy (pb/gev) σ / dp d CMS NLOJet++ C4 Anti-k t R = < 7 pb (3 ev) 6 y < 0.5 (x ) < y <.0 (x ) 4.0 < y <.5 (x ) 3.5 < y <.0 (x ).0 < y <.5 (x ).5 < y < 3.0 (x ) 0 3. < y < 4.7 (x )

5 Inclusive jets cross and 3eV Ratio to C CMS Data/(C NLO NP EWK) Data/(C NLO NP) ABM HERAPDF.5 MSW008 NNPDF3.0 otal exp. sys. unc. 8 ev y < 0.5 Open: L = 5.6 pb int 0. - anti-k t (R = 0.7) Filled: L int = 9.7 fb Jet p (GeV) Ratio to NLOJet++ C4.5 CMS R = 0.7 Anti-k t y < 0.5 Data HERAPDF.5 NNPDF3.0 MMH04 Exp. uncert. heo. uncert. - 7 pb (3 ev) Jet p (GeV) Predictions are in good agreement with data More can be learnt from these measurements see next slides A. Bermudez (DESY) April 07 5 / 5

6 Measurement of the triple-differential dijet cross section in pp collisions at s = 8eV arxiv: A. Bermudez (DESY) April 07 6 / 5

7 riple differential dijet cross y y y = y b = y + y d 3 σ dp,avg dy dy b = ɛl int,eff - p,avg leading jets average p - y = y y ) / - y b = (y + y ) / N p,avg y y b d 3 dp, avgdybdy * [pb/gev] CMS fb (8 ev) 0 yb < 0 y * < ( ) 0 yb < y * < ( ) 0 yb < y * < 3 ( ) yb < 0 y * < ( ) yb < y * < ( ) yb < 3 0 y * < ( 0) NLOJE++ (NLO EW NP) NNPDF 3.0 = p, e 0.3y* anti kt R = p, avg [GeV] - est of pqcd - Determination of coupling constant - Constraints on PDFs A. Bermudez (DESY) April 07 7 / 5

8 riple differential dijet cross - For mid-x ( partonic momentum fraction) regions data are well described - Boosted topologies (large-x) lacks from PDF information - Significantly small uncertainties at large-x potential constraints on PDF A. Bermudez (DESY) April 07 8 / 5

9 PDF constraints - Largest impact on the high-x region - PDF uncertainty from experimental, model, and parameterisation uncertainty α s extraction d σ dp dy α s ( LO) - α s an additional free parameter in the PDF fit α s (M Z ) = 9 ± 0.005(exp) (mod) (par) α s (M Z ) = (scale, refit) - α s measurement dominated by theory uncertainties - World average value: α s(m Z ) = 0.8 ± 0.00 xg(x, Q ) Rel. uncert. 4.0 HERAPDF method (Hessian) 3.5 CMS HERA I+II DIS HERA I+II DIS + CMS dijets 3.0 Q =.9GeV x 90 HERAPDF method (Hessian) 80 CMS HERA I+II DIS + CMS dijets HERA I+II DIS + CMS inc. jets 70 Q = 4 GeV x Rel. uncert. xg(x, Q ) A. Bermudez (DESY) April 07 9 / 5

10 Strong coupling constant from the measurement of inclusive multijet event cross sections in pp collisions at s = 8eV to be published A. Bermudez (DESY) April 07 / 5

11 Inclusive -jets, 3-jets and R 3 d σ d(h, /) = ɛl int,eff N event (H, /) H, /: leading jets average p, and scale of the event - Inclusive 3-jets, inclusive -jets were studied R 3 = dσ 3 α dσ s - JES is the dominant systematic uncertainty for σ (3-%) and σ 3 (3-8%) - R 3 theoretical and experimental uncertainties partially cancel (exp. uncertainties %) /) (pb/gev) dσ/d(h , - CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 n j C NP EWK n j 3 C NP H, / (GeV) A. Bermudez (DESY) April 07 / 5

12 Inclusive -jets, 3-jets and R 3 - Data are well described by the predictions - Uncertainties: large H, / PDF dominates in the upward direction, scale uncertainties in the downward direction - R 3 uncertainties significantly reduced. Ratios to NLO (C) CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 n j Data/(NP EWK) MSW008 NNPDF.3 Exp. Uncertainty heory Uncertainty Ratios to NLO (C) CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 R 3 Data/NP MSW008 NNPDF.3 Exp. Uncertainty heory Uncertainty Ratios to NLO (C) H, / (GeV) - CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 n j 3 Data/NP MSW008 NNPDF.3 Exp. Uncertainty heory Uncertainty H, / (GeV) H, / (GeV) A. Bermudez (DESY) April 07 / 5

13 α s extraction - Minimizing the χ between the experimental measurement and the theoretical predictions - Using MSW008 PDF: α s (M Z ) = 0.50 ± 0.00(exp) ± 0.003(PDF ) + ±0.005(NP) (scale) - Result for α s(m Z ) is in agreement with the world average value of α s(m Z ) = 0.8 ± 0.00 α S (Q) CMS R 3 preliminary, s = 8eV, α S (M ) = 0.50 z CMS R 3 preliminary, s = 8eV 0.6 CMS Incl.Jet, s = 8eV CMS R 3, s = 7eV 0.4 CMS Incl.Jet, s = 7eV CMS tt, s = 7eV CMS Preliminary CMS 3-Jet Mass, ALAS EEC, D0 Incl.Jet s s = 7eV = 7 ev D0 Angular Correlation H ZEUS World Avg α S (M ) = 0.8 ± z 0.00 R 3 Ratio to NLO (MMH04) CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 Data/NP C α s (M ) = 0. - Min. Value z C α s (M ) = 0.8 z C α s (M ) = Max. Value z H, / (GeV).5 - CMS Preliminary 9.7 fb (8 ev) R = 0.7 anti-k t y <.5 R 3 Data/NP MMH04 α s (M ) = Min. Value z MMH04 α s (M ) = 0.0 z MMH04 α s (M ) = Max. Value z Q (GeV) H, / (GeV) A. Bermudez (DESY) April 07 3 / 5

14 Measurement of angular and momentum distributions in multi-jet final states at s = 8eV and 3eV not yet released A. Bermudez (DESY) April 07 4 / 5

15 Multi-jets and 3eV - Interplay between parton showers and Matrix Elements - Soft and hard radiation sensitivity p 3 /p - Collinear and wide angle radiation sensitivity R 3 Criteria p 3 /p < 0.3 p 3 /p > 0.6 R 3 <.0 R 3 >.0 Radiation type soft p radiation hard p radiation small angle radiation large angle radiation A. Bermudez (DESY) April 07 5 / 5

16 Multi-jets and 3eV dσ d R 3 σ - CMS Preliminary.9 fb (3 ev) 3.5 Data 3 PYHIA (LOjets+PS) POWHEG (NLOjets+PS).5 MADGRAPH (LO4jets+PS) sys. sys. + sta. dσ d R 3 σ - CMS Preliminary.9 fb (3 ev) 3.5 Data 3 PYHIA (LOjets+PS) POWHEG (NLOjets+PS).5 MADGRAPH (LO4jets+PS) sys. sys. + sta p /p 3 < GeV < p < 500 GeV < p /p 3 5 GeV < p < 500 GeV MC / Data.3.. MC / Data All theoretical predictions show significant deviations from the measurements R 3 R 3 - Contribution from higher order ME calculations supplemented with parton showers are necessary for describing the hard region A. Bermudez (DESY) April 07 6 / 5

17 Measurements of inclusive -jet, 3-jet and 4-jet azimuthal correlations in pp collisions at 3eV to be published A. Bermudez (DESY) April 07 7 / 5

18 Dijet cross dσ, dσ, d φ, - Bin size 5 - Interesting tool to test theoretical predictions of multijet production processes - Region away from π is sensitive to hard radiation from ME ) - (rad dσ, d φ, σ, CMS 8 p > 00 GeV (x ) 7 00 < p < 00 GeV (x ) < p < 00 GeV (x ) < p < 800 GeV (x ) < p < 700 GeV (x ) < p < 600 GeV (x ) 400 < p < 500 GeV (x ) 300 < p < 400 GeV (x) 00 < p < 300 GeV fb Number of Jets Anti-k R = 0.4 (3 ev) PH-J + Pythia8 CUEP8M - Region close to π is sensitive to resummed contributions from PS Overall description of the data is achieved and understood - JES is the dominant systematic uncertainty (from 3% at π/ to 0.% at π) π / π/3 5π/6 π φ (rad), A. Bermudez (DESY) April 07 8 / 5

19 Dijet azimuthal angular correlations - MadGraph (up to 4 LO) describes well the data whereas P8 and Herwig++ ( LO) fail significantly - Powheg J and Powheg 3J are not able to describe the data better than P8 and Herwig++, even though they provide multi-leg ME - Herwig7, formally NLO but effectively 3 LO, gives a good description of the data - For this observable MC@NLO method of combining parton shower with the NLO parton level calculations has advantages compared to the POWHEG method A. Bermudez (DESY) April 07 9 / 5

20 Azimuthal angular correlations in high transverse momentum dijet events in high transverse momentum dijet events not yet released A. Bermudez (DESY) April 07 0 / 5

21 Dijet azimuthal angular correlations dσ, dσ, d φ, - In inclusive -jets and 3-jets events - Finer binning of - Detailed investigation of the resummation region ( φ 80 ) - esting the resummed predictions coming from different Parton Shower models - Studying matching and merging formalisms - Soft radiation interference and factorization breaking A. Bermudez (DESY) April 07 / 5

22 Dijet azimuthal angular correlations Ratio to Data CMS Preliminary < p < 300 GeV 400 < p 600 < p 800 < p p < φ 500 GeV [deg], < φ 700 GeV [deg], < φ 00 GeV [deg], > φ 00 GeV [deg], φ [deg], - MadGraph gives the best description, and starts to fail towards high p - P8 and Herwig++ perform similarly - Differences of up to % R=0.4 anti k t Inclusive -jets otal Syst. Unc Pythia8 CUEM Herwig++ CUEHppS MadGraph + P8CUEM fb 300 < p < 400 GeV 500 < p 700 < p 00 < p (3eV) < φ 600 GeV [deg], < φ 800 GeV [deg], < 00 φ GeV [deg], φ [deg], - Pythia8 and Herwig++ resum in the same way (only evolution variable differs) - here are correlations towards high p which are not captured either by the parton shower nor the multi-leg final state ME from MadGraph A. Bermudez (DESY) April 07 / 5

23 Dijet azimuthal angular correlations Ratio to Data CMS Preliminary < p < 300 GeV 400 < p 600 < p 800 < p p < φ 500 GeV [deg], < φ 700 GeV [deg], < φ 00 GeV [deg], > φ 00 GeV [deg], φ [deg], - MadGraph and Powheg 3J give the best description - Powheg J fails to describe the data - Biggest discrepancies in the last bin R=0.4 anti k t Inclusive -jets otal Syst. Unc PH-J + P8CUEM PH-3J + P8CUEM MadGraph + P8CUEM fb 300 < p < 400 GeV 500 < p 700 < p 00 < p (3eV) < φ 600 GeV [deg], < φ 800 GeV [deg], < 00 φ GeV [deg], φ [deg], - MadGraph and Powheg 3J, both go to up to 4 partons - Powheg J is effectively 3 LO A. Bermudez (DESY) April 07 3 / 5

24 Summary Inclusive jet cross s = 8 and s = 3eV - Sensitive to α s - Provides important PDFs constraints - QCD describes data within 4 orders of magnitude!! - Experimental uncertainties dominated by JES, unfolding and the integrated luminosity. Measurement of the triple-differential dijet cross section - est of pqcd - Determination of coupling constant and constraints on PDF Strong coupling constant from inclusive multijet events - est of QCD - R 3 is used to access extract α s Multi-jets and 3eV - Interplay of ME and PS when dealing with soft and hard scales - All theoretical predictions show significant deviations from the measurements Dijet azimuthal angular s = 3eV - Overall description of the data is achieved and understood - For this observable MC@NLO method of combining parton shower with the NLO parton level calculations has advantages compared to the POWHEG method Azimuthal angular correlations in high transverse momentum dijet events - Multi-leg final state MC Powheg 3J and Madgraph provide a good description of the data - hey start to fail towards high p were presumably non-trivial correlations appears A. Bermudez (DESY) April 07 4 / 5

25 hank you for your attention. A. Bermudez (DESY) April 07 5 / 5