Inclusive Jets in the Breit Frame in Deep- Inelastic Scattering T. Schörner-Sadenius, J. Standage ZEUS QCD Review Meeting DESY, 05 February 2004

DESY, 05/02/2004TSS: Inclusive Jets2 Outline  Introduction  The measurement  Lots of control-like plots … without too many words …  The correction function problem  Summary

DESY, 05/02/2004TSS: Inclusive Jets3 Introduction  Repetition of inclusive jets analysis in the Breit frame performed by Oscar Gonzalez in data from 96/97.  Q 2 > 125 GeV 2, jets cut in Breit only (E T >8,  from –2 to 1.8).  Single-differential cross-sections in E T, Q 2,  lab.  Extraction of strong coupling  Compared with the old measurement at least factor 3 in lumi  increase of statistical precision.  In addition maybe new ideas on parameter extraction?  New Analysis performed by Jeff Standage and TSS (second analysis – if ever there really is a difference ;-) ) …

DESY, 05/02/2004TSS: Inclusive Jets4  80-90pb-1 in data from 1998 to  Trigger selection: DST bit 12 (Q 2 > 80 GeV 2 )  Event selection:  >0 Sinistra candidates  Q 2 > 125 GeV 2  -0.7 < cos  had < 0.5  Ee’ > 10 GeV  y el 0.04  40 < E-pz < 70  -50 < zvtx < 50; chivtx < 10.  p T /sqrt(E T ) < 2.5  … The measurement See also Jeff’s presentation in Warsaw  Jet Selection  inclusive kT algorithm on mass -less zufos in Breit frame.  jet energy correction (Jeff); values obtained this far very similar to Oscar’s.  Some cleaning cuts (veto for events with jets close to electron / with backward jets)  E T Breit > 8 GeV, E T lab > 2.5 GeV  -2 <  Breit < 1.8

DESY, 05/02/2004TSS: Inclusive Jets5  JS and TSS use standard Orange job;  Data: DST bit selection  MC: no selection at all, hadron level information from some version of get_hadsys (how many different are around?)  the origin of “correction function problem” (see later)?  “Offline” selection:  JS: fortran based, standard boost and jet algo routines  TSS: based on ROOT, boost and jet algo borrowed from (different) sources … .. After some long fights with cuts and the order in which cuts are applied (before/after corrections) etc.: Complete agreement on 20k MC test sample (except for one event which suffers from different precisions in fortran and ROOT/C++). Analysis Setups Nice complementarity

DESY, 05/02/2004TSS: Inclusive Jets6 Q2Q2 Q2Q2 yy E-p z xx Kinematics Good agreement data-MC (normalised to 1) Electron methodDA method

DESY, 05/02/2004TSS: Inclusive Jets7 The Electron Good agreement pTpT E thetaphi

DESY, 05/02/2004TSS: Inclusive Jets8 Calibration and technicalities Seems to be okay p Tmiss prl p Tmiss p Tmiss perp p Tbal

DESY, 05/02/2004TSS: Inclusive Jets9 Zufos, zvtx Nice description of data pTpT etaphi N E zvtx

DESY, 05/02/2004TSS: Inclusive Jets10 Selected Jets (lab) Agreement okay?  Distributions in Breit similar.  Also reasonable on linear scale.  Number of jets? pTpT etaN E

DESY, 05/02/2004TSS: Inclusive Jets11 Q2Q2 ETET  lab  Breit Q2Q2 ETET  lab  Breit Correction Functions … this is where the problems start … Uncorrected jetsCorrected jets

DESY, 05/02/2004TSS: Inclusive Jets12 Migrations … nothing unusual … Efficiencies and purities (or stabilities) basically everywhere okay. Values between 40 and 90%. These corrections are observed with two different MC samples, two different get_hadsys methods and two different offline analyses … Any idea where it could come from? Q2Q2 ETET  Breit  lab

DESY, 05/02/2004TSS: Inclusive Jets13 Final Distributions normalized to unity  Shapes data / det. level MC compare well …  Hadron level …? Q2Q2  lab ETET  Breit

DESY, 05/02/2004TSS: Inclusive Jets14 Conclusions  Repetition of inclusive jet analysis should in principle be straight forward. The detector level seems understood – nice agreement between data and MC for basically all relevant quantities.  However, very large correction functions are observed, which one would not expect judging from the previous analysis.  Juan will run his code over our MC … looking very much forward to hearing from him!  Aim / Hope: … to still make it for a preliminary for DIS Jeff should be back at DESY soon.