Tanja Susa Kreso Kadija Tome Anticic Vedran Nikolic Production of hyperon and hyperon resonances in p+p collisions (and status of pA analysis) Tanja Susa Kreso Kadija Tome Anticic Vedran Nikolic Rudjer Boskovic Institute Zagreb, Croatia NA49 collaboration meeting, CERN, 2008

Inclusive cross section But Nbeam hard to determine Instead, use ratio N trigger/Nbeam and N trigger ≈1% difference Used before Use exact formula tatjana.susa@cern.ch

Negligible difference Trigger cross section From full and empty data sample Take into account beam attenuation Before ≈2% difference Negligible difference p+p pion paper tatjana.susa@cern.ch

Ntrigger sF sE s2 s1 x2 x1 l Very complicated… From full and empty data sample Take into account beam attenuation Very complicated… ≈1% difference sF sE s1 s2 x1 x2 l tatjana.susa@cern.ch

nx nx = nxdet CF VENUS . nx number of particles x produced in hydrogen nxdet ... number of detected particles x (xi/v0) after vertex cuts CF ... correction factor: branching ratio acceptance and efficiency v0/xi cuts trigger loss correction vertex cuts losses VENUS . tatjana.susa@cern.ch

Data sets All p+p data sets Changes with respect to old analysis Improve geometry and correct residual distortions 1996 1999 2000 2001 2002 1.03 M 1.21 M 2.67 M 0.67 M 2.84 M Correct bugs in reconstruction clients R3D tpc_error Open cuts and/or correct bugs in V0 fitter/finder and Ξ finder and use new 13 par. Ξ fitter tatjana.susa@cern.ch

all tracks are +- 3 s (dE/dX)  cuts (by)2 + (bx/2)2 < x2 proton p  rap < -2.25 z - zmain < 0 cm x = 1 -2.35 < rap < -2.25 z - zmain < 1 cm x = 1 all tracks are +- 3 s (dE/dX) -1.75 < rap < 0.25 z - zmain < 3 cm x = 1 2 MeV/bin 0.25< rap < 0.75 z - zmain < 5 cm x = 1 about 125k 0.75 < rap < 1.25 z - zmain < 5 cm x = 0.25 1.25 < rap < 1.75 z - zmain < 10 cm x = 0.25 Minv(pπ-)[GeV] tatjana.susa@cern.ch

 signal comparison 96 + 99 + 00 data sets New Old about 68 k 2 MeV/bin 2 MeV/bin New Old Minv(pπ-)[GeV] Minv(pπ-)[GeV] about 68 k about 35k tatjana.susa@cern.ch

Both include losses due  correction factors 1./CF New Old rat Both include losses due to the vertex cut tatjana.susa@cern.ch

 signal - rapidity dσ/dpt[mb/GeV] dσ/dy[mb] w/o feed. corr. pt[GeV] tatjana.susa@cern.ch

 rapidity comparison feed. corr. dσ/dy[mb] new old rapidity tatjana.susa@cern.ch

 pt comparison y=-1.5 y=-1 y=-0.5 y=0 new old y=1.5 y=1 y=0.5 tatjana.susa@cern.ch

 signal – inv. xf dσ/dpt[mb/GeV] dσ/dy[mb] w/o feed. corr. pt[GeV] tatjana.susa@cern.ch

 inv. xf comparison feed. corr. dσ/dy[mb] new old xf tatjana.susa@cern.ch

Comparison with world data tatjana.susa@cern.ch

Some quality checks on the new data Check sensitivity of L yield on behaviour of: Vertex cut S4 trigger loss Geometry and residual distorsion corrections Stability across years tatjana.susa@cern.ch

Vertex cut CUT nev/nevorig vtx. fitted 81% ≈ 18% of data: background interactions CUT nev/nevorig vtx. fitted 81% |z-zcent| < 9 cm 60% (|z-zcent| < 5.5 cm, 96 ) x2+y2 < 1 cm2 60% Loss of the p+p event ≈ 25% (10% geom. effect) Corrected with VENUS tatjana.susa@cern.ch

Non-reconstructed vertex (2000) rec. vtx. non-rec. vtx. FULL # of Λ in hydrogen nnorec/nrec ≈ 3.1% EMPTY tatjana.susa@cern.ch

Non-reconstructed vertex (2002) rec. vtx. non-rec. vtx. FULL # of Λ in hydrogen nnorec/nrec ≈ 1.2% EMPTY tatjana.susa@cern.ch

Non-reconstructed vertex (MC) rec. vtx. non-rec. vtx. minv(pπ-)[GeV] # of Λ in hydrogen nnorec/nrec ≈ 1.8 % Good agreement with data tatjana.susa@cern.ch

In ideal case, FT-ET should be flat. Good agreement. Systematics on Reconstructed vertex VENUS corrected |z-znom|[cm] σΛ/σΛ(9 cm cut) FT FT-ET All rapidities |y| < 0.25 In ideal case, FT-ET should be flat. Good agreement. Systematics on the order of about 1-2 % tatjana.susa@cern.ch

Reconstructed vertex (MC) Data (FT -ET) VENUS (MB) z[cm] n Additional check Good agreement of data with MC tatjana.susa@cern.ch

 trigger loss (VENUS S4 correction) S4 correction comparison between VENUS and data (2002 using GAP TPC data) data VENUS Good agreement tatjana.susa@cern.ch

Stability across the years Midrapidity  yield ds/dy feed. corr. year Max difference 1996 (7%) tatjana.susa@cern.ch

Geometry and residual distortion correction w/o geom.corr. old V0 new V0 with geom. corr. Reconstructed 2000 data w/o geom. and res.corr. improved clients included MC data not corrected for residual distortion Run both old & new V0, Ξ finders/fitters mb Analysis type pt [GeV] Yield stable, geom., res. corr. and V0 finder/fitter not a source of differences tatjana.susa@cern.ch

pA analysis status Geometry/Residuals corrected for 1999 and 2001 Data run for 1999 2001 in progress Analysis proceeding 1999 2001 1 285 000 events Centralities: 1 316727 2 325707 3 41948 4 21670 7 334971 1 500 000 events Centralities: 1 575296 3 497676 7 487173 tatjana.susa@cern.ch

1999 pA geometry After corrections in: Geometry Residuals BPD x residuals (cm) Before y residuals (cm) z (cm) tatjana.susa@cern.ch

1999 pA impact paramters Main vertex tracks L cm cm cm cm x impact parameter cm y impact parameter cm cm cm Main vertex tracks L tatjana.susa@cern.ch

L invariant mass About 15% more Ls GeV tatjana.susa@cern.ch

Conclusion L analysis in good progress Systematic influence found small for: S4 main vertex geometry and distortion correction V0 finder/fitter pA analysis in progress tatjana.susa@cern.ch