Progress on CTEQ-TEA PDFs

Transcription

1 Progress on CTEQ-TEA PDFs Tie-Jiun Hou Xinjiang University for the CTEQ-TEA (Tung et al) collaboration April 17, 2018 DIS2018

2 CTEQ-TEA group CTEQ -- Tung et al. (TEA) in memory of Prof. Wu-Ki Tung, who established CTEQ Collaboration in early 90's. Current members: Sayipjamal Dulat, Tie-Jiun Hou, Ibrahim Sitiwaldi (Xinjiang U.) Jun Gao (Shanghai Jiaotong U.) Marco Guzzi (Kennesaw State U.) Pavel Nadolsky, Tim Hobbs, Keping Xie, Bo-Ting Wang (Southern Methodist U.) Joey Huston, Jon Pumplin, Carl Schmidt, Dan Stump, Jan Winter, C.-P. Yuan (Michigan State U.) 2

3 Data sets included in CT17pre Start with CT14HERA2 (HERAII combined data released after publication of CT14) Use as much relevant LHC data as possible using applgrid/fastnlo interfaces to data sets, with NNLO/NLO K-factors, including incl. Jet data, or fastnnlo tables in the case of top pair production Implement a parallelization of the global PDF fitting to allow for faster turn-around time PDFSense (see Fred Olness s talk) to determine which data will have impact on global PDF fit epump (see Tie-Jiun Hou s talk) on exploring the impact of data prior to global fit 3

4 Fitting code changes 4

5 LHC data sets included in CT17pre LHCb Z (W) rapidity (muon rapidity) at 7 (applgrid); 8 TeV Z rapidity (applgrid) LHCb heavy flavor (applgrid) (to be added), SACOT-chi, base on Xie, Campbell, Nadolskey, 2018 ATLAS W/Z lepton(s) rapidity at 7 TeV (applgrid) ATLAS 8 TeV DY (applgrid) ATLAS 7 TeV Z p (applgrid) T ATLAS 8 Z p, as a function of mass (applgrid) T CMS Z p,as a function of y, at 8 TeV (applgrid) T CMS W lepton rapidity (asymmetry) at 8 TeV (applgrid); CMS W,Z p at 8 TeV (applgrid) T CMS inclusive jet cross section at 7,8 TeV with R=0.7 (fastnlo) ATLAS inclusive jet cross section at 7 TeV with R=0.6 (applgrid) ATLAS and CMS 7,8 TeV tt differential distributions (fastnnlo) including double differential from CMS at 8 TeV (work in progress) ATLAS low mass/high mass Drell-Yan at 7 TeV (applgrid) CMS low mass/high mass DY at 8 TeV (applgrid) There is a lot of new data, but there is also a lot of old data already in the fit, that continues to have an impact, and will tend to dilute the impact of new data. 5

6 How sensitive is an experiment to a PDF? Can we know it before doing the global fit? PDFsense predicts that the CMS data will have the largest impact PDFSense estimates ranking of strength of sensitivities of experimental data sets to PDF flavors without for example, (re-)doing the full global fit HERAII, CMS impact on global fit requires both correlation jets provide information on and sensitivity gluon and on Higgs σ See Fred Olness talk Sensitivity to the PDF error on σ ( pp HX ) at 14 TeV see for example

7 epump (Error PDF Updating Method Package) epump is a set of classes, functions, etc. for analyzing the impact of new data on the PDF predictions and uncertainties, in the Hessian method. It assumes quadratic dependence of the global c2 function on the parameters, and linear dependence of the observables on the parameters. It allows for the inclusion of a dynamical tolerance in each of the original Hessian eigenvector directions. Extensively cross-checked against CT14 global fits UpdatePDFs computes updated prediction and uncertainties by including new data. OptimizePDFs generate particular eigenvector sets respect to a set of observables. A subset of the eigenvector sets can reproduce the prediction and saving time for calculation. See Tie-Jiun Hou talk 7

8 Existing comparisons of 3 PDFs (CT14NNLO, MMHT2014nnlo, NNPDF3.1nnloas0118) 3 PDF groups are compatible; can new generation of PDFs improve precision? 8 Especially for gluon distribution in Higgs mass range.

9 CMS jet production From PDFSense, expect CMS jet data, both at 7 TeV and 8 TeV to have impact, in fact the highest impact, primarily on gluon distribution 9

10 pt vs pt1 Non-negligible difference between scale choice of pt (inclusive jet pt) and lead jet pt (pt1) for NNLO predictions Nominal choice by CTEQ-TEA is pt In fact, fitted gluon is almost exactly the same in kinematic region where difference is important There is a resilience in the global fit due to other data present in this kinematic region (and evolution) 10

11 Top Quark Pair differential distributions y t t distribution gives the strongest impact to PDF for both CMS and ATLAS 8TeV. Impact for ttbar distributions is consistent with jet on gluon-pdf, through jet data provide stronger constraint. We choose to include normalized (nor.) CMS y t t and absolute (abs.) ATLAS y ave distributions in CT17pre. Data CMS 8 nor. dsig/dpt Npts 8 Chi^2(no fit) Chi^2/Npts CMS 8 nor. dsig/dya CMS 8 nor. dsig/dmtt CMS 8 nor. dsig/dytt ATLAS 8 abs. dsig/dpt ATLAS 8 abs. dsig/dya ATLAS 8 abs. dsig/dmtt ATLAS 8 abs. dsig/dytt O O 11

12 Goodness of CT17pre Fit LHCb 7 (W,Z) ATLAS 8 (ZpT + hmdy) CMS7jet Residual ( T D shifted σ 2 stat +σ 2 unc. sys LHCb 8 (W,Z) CMS8jet ) CMS 8 nor. ttb ytt ATLAS 8 abs. ttb yavet 12

13 Preview of CT17pre (g-pdf) Improvement in gluon uncertainty for x around 0.2 dominated by the CMS 8 TeV jet data. Reduction of gluon central PDF for x around 0.2 is due to ATLAS 8 TeV ZpT, CMS 8 TeV jet data and ttbar distributions, ATLAS and CMS. ATLAS8ZpT,CMS7/8jet ATLAS8ZpT,CMS8jet 13

14 Preview of CT17pre (u-pdf) The new LHC DY data has some impact to u, while the reduction of central PDF in u-pdf is mainly due to the LHCb 8 TeV WZ data. LHCb8(W,Z) 14

15 Preview of CT17pre (d-pdf) Improvement of uncertainty at x around 0.2 mainly comes from CMS 8 TeV jet data. Both the 7 and 8 TeV LHCb ZW data slightly increase d-pdf at x around 0.2. Small reduction of central d-pdf at x around 10^-3 is mainly due to the LHCb 8 TeV WZ data. CMS8jet LHCb8(W,Z) LHCb7/8(W,Z) 15

16 Preview of CT17pre (s-pdf) The new LHC DY and jet data have some effect on SPDF, but mainly due to LHCb 8 TeV WZ data. Larger central S-PDF, though still consistent with CT14HERA2. LHCb8(W,Z) 16

17 Preview of CT17pre (ubar and dbar PDFs) 17

18 Preview of CT17pre (d/u and dbar/ubar) LHCb8(W,Z) LHCb8(W,Z) 18

19 Preview of CT17pre (CT17pre,MMHT2014nnlo,NNPDF31nnloas0118) Q=100 GeV Three PDF groups are getting closer, though still consistent with CT14NNLO. 19

20 Summary Detailed investigation of the LHC 7 and 8 TeV vector boson, jet, ttbar production data suggests their mild impact on the central fits, PDF uncertainties, and precision EW observables, as compared to the CT14HERA2 NNLO data set. We notice the potential of the future ATLAS/CMS jet data, together with other LHC processes, for strengthening the constraints on the g, s, ubar, and dbar PDFs with modest improvements in experimental systematics and full implementation of NNLO jet cross sections. Three PDF groups with CT17pre are getting closer, through still consistent with CT14NNLO. PDFSense code has been released, together with many comparisons. (See Fred Olness s Talk) epump paper is in preparation, and epump code will be made public available at (See Tie-Jiun Hou s Talk) CT17 PDFs will be used as a framework for new developments in the photon PDF 20