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Probing QCD and hadron physics: highlights of experimental results

Probing QCD and hadron physics: highlights of experimental results. Chiara Roda Universita` and INFN of Pisa ICHEP2014 - Valencia. Why bother ?. Understanding/testing the QCD theory of SM in a new kinematic range never explored before (LHC) at many different scales (HERA, TeVatron, LHC)

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Probing QCD and hadron physics: highlights of experimental results

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  1. Probing QCD and hadron physics: highlights of experimental results Chiara RodaUniversita` and INFN of Pisa ICHEP2014 - Valencia C.Roda – Universita` & INFN Pisa

  2. Why bother ? • Understanding/testing the QCD theory of SM • in a new kinematic range never explored before (LHC) • at many different scales (HERA, TeVatron, LHC) • in a variety of initial states: ep, ppbar, pp C.Roda – Universita` & INFN Pisa

  3. Why bother ? • Understanding/testing the QCD theory of SMin a new kinematic range never explored before (LHC) • at many different scales (HERA, TeVatron, LHC) • in a variety of initial states: ep, pp, pp LHC collider pp - √s=7-8 TeV Operating from 2010 Tevatron collider pp - √s=1.8 - 1.96 TeV Operated 1987-2011 HERA collider e±p - √s=225-320 GeV Operated 1992-2007 C.Roda – Universita` & INFN Pisa

  4. Why bother ? • Understanding/testing the QCD theory of SMin a new kinematic range never explored before (LHC) • at many different scales (HERA, TeVatron, LHC) • in a variety of initial states: ep, ppbar, pp Our level of understanding and modeling of the QCD interactions has direct impact on the potential we have for precision measurements and discovery Largest syst. For Higgs cross-section is from σ(ggF): 7% scales / 7% PDFs W/Z+jet is often one of the largest background to top-quark, SUSY, Higgs and exotic searches. C.Roda – Universita` & INFN Pisa

  5. The ingredients in the predictions… C.Roda – Universita` & INFN Pisa

  6. The ingredients in the predictions… Hard Scattering and parton shower: fixed order NLO partonic calculations (NLOJET++,MCFM,BlackHat), LO+PS (Pythia, Herwig), High multi. LO+PS (Alpgen, Sherpa, Madgraph,…). State of the art: NLO+PS (MC@NLO+PS, POWHEG+PS, MEPS@NLO) C.Roda – Universita` & INFN Pisa

  7. The ingredients in the predictions… Hard Scattering and parton shower: fixed order NLO partonic calculations (NLOJET++,MCFM,BlackHat), LO+PS (Pythia, Herwig), High multi. LO+PS (Alpgen, Sherpa, Madgraph,…). State of the art: NLO+PS (MC@NLO+PS, POWHEG+PS, MEPS@NLO) PDF: CTEQ/CT, NNPDF, MSTW, ABM, HERAPDF… Differences: data used the fit, αsvalue, treatment of errors, parameterization… C.Roda – Universita` & INFN Pisa

  8. The ingredients in the predictions… Hard Scattering and parton shower: fixed order NLO partonic calculations (NLOJET++,MCFM,BlackHat), LO+PS (Pythia, Herwig), High multi. LO+PS (Alpgen, Sherpa, Madgraph,…). State of the art: NLO+PS (MC@NLO+PS, POWHEG+PS, MEPS@NLO) Mostly anti-kT – various cone sizes PDF: CTEQ/CT, NNPDF, MSTW, ABM, HERAPDF… Differences: data used the fit, αsvalue, treatment of errors, parameterization… Measurements are unfolded at particle level to be compared with predictions C.Roda – Universita` & INFN Pisa

  9. The ingredients in the predictions… Hard Scattering and parton shower: fixed order NLO partonic calculations (NLOJET++,MCFM,BlackHat), LO+PS (Pythia, Herwig), High multi. LO+PS (Alpgen, Sherpa, Madgraph,…). State of the art: NLO+PS (MC@NLO+PS, POWHEG+PS, MEPS@NLO) A sizeable contribution in understanding our measurements also comes from the quality of modeling of soft hadronic physics… no results in this talk but the measurements are used for the tuning of MC used. Mostly AntikT – various cone sizes PDF: CTEQ/CT, NNPDF, MSTW, AMB, HERAPDF… Differences: data used the fit, αsvalue, treatment of errors, parameterization… Measurements are unfolded at particle level to be compared with predictions C.Roda – Universita` & INFN Pisa

  10. Jet cross-sections Just two examples among the many results … C.Roda – Universita` & INFN Pisa

  11. STDM-2013-11 CMS-PAS-FSQ-12-031 CMS-PAS-SMP-12-012 Inclusive cross-section @ 8 TeV 8 TeV 16 orders of magnitude Low pile-up data to extend to the low pT range down to 20 GeV and |y|<4.7 20 Gev – 2 TeV LHC data allows pQCD tests in a new kinematic regime – extended in pT and y Covers 16 orders of magnitude / two jet sizes Reference prediction: NLOJET + NNPDF2.1 but other PDF tested C.Roda – Universita` & INFN Pisa

  12. More challenge… higher multiplicities 3-jet |Y*|=|y1-y2| + |y2-y3| + |y1-y3| 9 orders of magnitude Mjjj = [0.38,1.2] TeV Distributions are sensitive both to jet pT and to the angular distributions Data are compared to many different PDFs, different jet sizes Data can be used to constrain PDFs (exp and theory uncertainties similar) C.Roda – Universita` & INFN Pisa

  13. arXiv:1406;0324 Jet with different sizes … what we learn Inclusive cross-section ratio R(0.5,0.7) = [dσ(0.5)/dpT]/[dσ(0.7)/dpT] Variable sensitive to pertubative radiation, hadronization, underlying-event C.Roda – Universita` & INFN Pisa

  14. arXiv:1406;0324 Jet with different sizes … what we learn R(0.5,0.7) = [dσ(0.5)/dpT]/[dσ(0.7)/dpT] C.Roda – Universita` & INFN Pisa

  15. arXiv:1406;0324 Jet with different sizes … what we learn R(0.5,0.7) = [dσ(0.5)/dpT]/[dσ(0.7)/dpT] LONLO C.Roda – Universita` & INFN Pisa

  16. arXiv:1406;0324 Jet with different sizes … what we learn R(0.5,0.7) = [dσ(0.5)/dpT]/[dσ(0.7)/dpT] LONLO NLONLO*NP C.Roda – Universita` & INFN Pisa

  17. arXiv:1406;0324 Jet with different sizes … what we learn R(0.5,0.7) = [dσ(0.5)/dpT]/[dσ(0.7)/dpT] Best description need NLO and parton shower are needed to describe correctly the ratio … C.Roda – Universita` & INFN Pisa

  18. what we learned from jets … Inclusive and multiple jet cross-sections have been measured in ATLAS and CMS extending the previously tested kinematic range Good agreement is found with NLOJET++ prediction Various PDF tested and most of them show good data description with exception of HERAPDF and in particular ABM11 which show disagreement in some kinematic regions POWHEG+PYTHIA is found to give the best description of inclusive jet cross-section for different jet sizes Measurements are used as input to constrain gluon PDFs C.Roda – Universita` & INFN Pisa

  19. α strong measurement C.Roda – Universita` & INFN Pisa

  20. CMS-PAS-SMP-12-028 CMS-PAS-SMP-12-027 arXiv 1406:470 αs measurement World average (2014) αs(MZ)= 0.1185 ± 0.0006 (0.5%) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP C.Roda – Universita` & INFN Pisa

  21. CMS-PAS-SMP-12-028 CMS-PAS-SMP-12-027 arXiv 1406:470 αs measurement World average (2014) αs(MZ)= 0.1185 ± 0.0006 (0.5%) CMS Most recent: inclusive jet (5%) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP C.Roda – Universita` & INFN Pisa

  22. CMS-PAS-SMP-12-028 CMS-PAS-SMP-12-027 arXiv 1406:470 αs measurement World average (2014) αs(MZ)= 0.1185 ± 0.0006 (0.5%) CMS Most recent: inclusive jet (5%) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP H1 most recent αs extraction from inclusive and multjet cross-section. Best precision is reached from fit to normalised multijet cross sections: 0.0036 (scale) exp. unc.0.7% C.Roda – Universita` & INFN Pisa

  23. CMS-PAS-SMP-12-028 CMS-PAS-SMP-12-027 arXiv 1406:470 αs measurement World average (2014) αs(MZ)= 0.1185 ± 0.0006 (0.5%) CMS Most recent: inclusive jet (5%) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP H1 most recent αs extraction from inclusive and multjet cross-section. Best precision is reached from fit to normalised multijet cross sections: All measurements consistent with world average Fantastic proof of αs(Q) running up to the TeV region 0.0036 (scale) exp. unc.0.7% C.Roda – Universita` & INFN Pisa

  24. CMS-PAS-SMP-12-028 CMS-PAS-SMP-12-027 arXiv 1406:470 αs measurement World average (2014) αs(MZ)= 0.1185 ± 0.0006 (0.5%) CMS Most recent: inclusive jet (5%) https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP H1 most recent αs extraction from inclusive and multjet cross-section. Best precision is reached from fit to normalised multijet cross sections: All measurements consistent with world average Fantastic prove of αs(Q) running up to the TeV region 0.0036 (scale) exp. unc.0.7% C.Roda – Universita` & INFN Pisa

  25. Parton Distribution Functions C.Roda – Universita` & INFN Pisa

  26. H1prelim14-041; ZEUS-prel-14-005 PDF @ HERA (ZEUS+H1) • HERA – most important data to measure the PDF • HERAPDF are based solely on the HERA ep data e+p - NC HERAPDF2.0 set recently obtained: use the full HERAI and HERAII dataset Larger HERAII lumi yields significant improvement in precision at high x, Q2 region • Consistent data • Large reduction in uncertainties C.Roda – Universita` & INFN Pisa

  27. H1prelim14-042 ZEUS-prel-14-007 PDF – HERA2.0 PDF set How does HERAPDF1.5 compare to new 2.0 NNLO ? • Shapes are similar • Gluon and sea at low and high x have smaller uncertainty and they become slightly softer • Valence at high x has also smaller uncertainty C.Roda – Universita` & INFN Pisa

  28. CMS-PAS-SMP-12-028 The gluon PDF… and input from LHC PDF fits using only data from experiments with lower momentum transfer than available at the LHC have large uncertainties for the LHC kinematic region. Data from LHC start to be precise enough to be used for PDF constraint C.Roda – Universita` & INFN Pisa

  29. CMS-PAS-SMP-12-028 The gluon PDF… and input from LHC PDF fits using only data from experiments with lower momentum transfer than available at the LHC have large uncertainties for the LHC kinematic region. Gluon PDF constraint from CMS with 7 TeV inclusive jet cross-section Data from LHC start to be precise enough to be used for PDF constraint • CMS fit a harder gluon, with respect to the fit using HERA alone (same results from ATLAS on lower stat. sample) • • Fractional uncertainty is smaller at high x, partly due to increased prediction • • Measurements are systematic limited at lower jet pT, dominated by the JES uncertainty C.Roda – Universita` & INFN Pisa

  30. CMS-PAS-SMP-12-028 The gluon PDF… and input from LHC PDF fits using only data from experiments with lower momentum transfer than available at the LHC have large uncertainties for the LHC kinematic region. Gluon PDF constraint from CMS with 7 TeV inclusive jet cross-section Very active field more results expected soon… Data from LHC start to be precise enough to be used for PDF constraint • CMS fit a harder gluon, with respect to the fit using HERA alone (same results from ATLAS on lower stat. sample) • • Fractional uncertainty is smaller at high x, partly due to increased prediction • • Measurements are systematic limited at lower jet pT, dominated by the JES uncertainty C.Roda – Universita` & INFN Pisa

  31. Inclusive γ, γ+jet, γ+HF C.Roda – Universita` & INFN Pisa

  32. Isolated photon production • Photon is used as clean/uncolored probe for underlying parton-parton interaction • Test pQCD but also sensitive to non-prompt photons produced in fragmentation processes • Provide information on PDFs Tevatron LHC – 14 TeV C.Roda – Universita` & INFN Pisa

  33. Phys.Rev.D 89, 052004 (2014) ATL-PHYS-PUB-2013-018 Isolated photon production 7 TeV No γ from fragmentation • New measurement extend the range from 0.1-1TeV ET and 5 orders of magnitude • NLO prediction (Jetphox+MSTW or CT10) describe very well the data up to high ET • Data demonstrate the need to have fragmentation photon to describe the data Data is also used to verify the sensitivity to the gluon-PDF and show some tensions with all PDFs expectially with ABM shows a too soft gluon-PDF. Measurement limited by scale uncertainty, NNLO prediction would help. C.Roda – Universita` & INFN Pisa

  34. CMS-PAS-SMP-14-005 Isolated photon production 8 TeV Njet ≥1 4 times more statistics  halving of statistical uncertainty Comparison is at LO … but NLO is coming • New measurement extend the range from 0.1-1TeV ET and 5 orders of magnitude • NLO prediction (Jetphox+MSTW or CT10) describe very well the data up to high ET • Data demonstrate the need to have fragmentation photon to describe the data Data is also used to verify the sensitivity to the gluon-PDF and show some tensions with all PDFs expectially with ABM shows a too soft gluon-PDF. Measurement limited by scale uncertainty, NNLO prediction would help. C.Roda – Universita` & INFN Pisa

  35. Phys.Rev.D 89, 074001 (2014) FERMILAB-PUB-14-135-E γ+bb cross-section – D0 • Higher uncertainty in the prediction than for LF jets • Direct access to b-quark PDF • Isolation to limit photon from fragmentation • Very different process contribution for Tevatron and LHC • NLO calculation and kT factorization/NLO approach show good agreement with data. • NLO calculation has smaller scale uncertainty • PYTHIA fails both shape and rate • SHERPA fails at low pT C.Roda – Universita` & INFN Pisa

  36. W/Z+jets C.Roda – Universita` & INFN Pisa

  37. A deep look at W+jet – ATLAS & CMS A detailed comparison on a high statistics sample and in a large kinematics range  precious information to validate/tune the predictions. Tested variables: 1st , 2nd, 3rd 4th-leading jet pT and η, HT,ST (Sum pT including or not lepton and neutrino), angular separation of jets, invariant mass of lead-subleading jets. Inclusive and exclusive distributions… Predictions: NLO calculations, resummation calculations, MC generators NLO,LO + PS C.Roda – Universita` & INFN Pisa

  38. CMS-PAS-SMP-12-023 ATLAS-CONF-2014-035 A deep look at W+jet – ATLAS & CMS Jet multiplicity C.Roda – Universita` & INFN Pisa

  39. CMS-PAS-SMP-12-023 ATLAS-CONF-2014-035 A deep look at W+jet – ATLAS & CMS Jet multiplicity Jet multiplicity well reproduced up to ≥7 jets on 5 order of magnitudes ! Best overall description NLO+PS (BlackHat+Sherpa) with some exception for high HT, ST distributions. C.Roda – Universita` & INFN Pisa

  40. CMS-PAS-SMP-14-009 Double differential Z+jet @ 8 TeV 30 First double differential measurement Z+jet Jet up to |η|<4.7 – 30 < pT<550 GeV Largest experimental uncertainty JES Predictions: MadGraph norm.NNLO / Sherpa2 (NLO 1j,2j) C.Roda – Universita` & INFN Pisa

  41. CMS-PAS-SMP-14-009 Double differential Z+jet @ 8 TeV First double differential measurement Z+jet Jet up to |η|<4.7 – 30 < pT<550 GeV Largest experimental uncertainty JES Predictions: MadGraph norm.NNLO / Sherpa2 (NLO 1j,2j /LO<=4j) MadGraph overshoot for pTjet > 100 GeV Reasonable description from Sherpa2, some regions to investigate C.Roda – Universita` & INFN Pisa

  42. CMS-PAS-SMP-14-005 ATLAS-CONF-2014-034 Boson+jets production ratios Ratios allows to reduce experimental systematic uncertainties Ratio is studied in inclusive and exclusive distributions for Njet≥3 C.Roda – Universita` & INFN Pisa

  43. CMS-PAS-SMP-14-005 ATLAS-CONF-2014-034 Boson+jets production ratios Ratios allows to reduce experimental systematic uncertainties Ratio is studied in inclusive and exclusive distributions of Njet=3 W+jet/Z+jet vs pT jet leading Njet≥1 - 7 TeV C.Roda – Universita` & INFN Pisa

  44. CMS-PAS-SMP-14-005 ATLAS-CONF-2014-034 Boson+jets production ratios Ratios allows to reduce experimental systematic uncertainties Ratio is studied in inclusive and exclusive distributions of Njet=3 W+jet/Z+jet vs pT jet leading Njet≥1 - 7 TeV Z+jet/γ+jet vs pT boson Njet≥1 - 8 TeV C.Roda – Universita` & INFN Pisa

  45. CMS-PAS-SMP-14-005 ATLAS-CONF-2014-034 Boson+jets production ratios Ratios allows to reduce experimental systematic uncertainties Ratio is studied in inclusive and exclusive distributions of Njet=3 W+jet/Z+jet vs pT jet leading Njet≥1 - 7 TeV Z+jet/γ+jet vs pT boson Njet≥1 - 8 TeV Flattens at high transferred transverse momentum LO prediction 10% off in norm / good in shape Detailed test of ratios with respect to NLO/LO predictions C.Roda – Universita` & INFN Pisa

  46. W/Z+HF C.Roda – Universita` & INFN Pisa

  47. JHEP 05 (2014) 068 JHEP 02(2014)013 W+charm - LHC • Probes the strange content of the proton • contribution from d quark about ~10% (Cabibbo suppressed) • Different PDFs assume different level of suppression of s-quark w.r. to d-quark sea. C.Roda – Universita` & INFN Pisa

  48. JHEP05(2014)068 arXiv:1402.6263 arXiv:1312.6283 W+c – LHC ATLAS  no s-sea suppression w.r. to light flavour sea

  49. JHEP05(2014)068 arXiv:1402.6263 arXiv:1312.6283 W+c – LHC ATLAS  no s-sea suppression w.r. to light flavour sea CMS  consistent with s-sea suppression

  50. JHEP05(2014)068 arXiv:1402.6263 arXiv:1312.6283 W+c – LHC ATLAS  no s-sea suppression w.r. to light flavour sea CMS  consistent with s-sea suppression Fit s-quark PDF: HERAPDF including W+c data

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