Baryon Meson Production in Jets and Ridges Maria

Baryon – Meson Production in Jets and Ridges Maria Cristina Suarez High Energy and Heavy Ion Experimental physics at UIC Physics Fest 2008 University of Illinois at Chicago Maria Cristina Suarez University of Illinois at Chicago 1 / 100 February 28 2008

Outline ¢ ¢ ¢ Physics Fest at UIC Experiment Motivation Analysis data Preliminary results Summary Maria Cristina Suarez University of Illinois at Chicago 2 / 100 February 28 2008

Working Team Marty Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 3 / 100 February 28 2008

RHIC v The Relativistic Heavy Ion Collider was built with the intent on probing collisions with heavy nuclei at relativistic speeds. v High energy density matter is created and is studied. v Search for existence of QGP v RHIC can collide heavy ions at energies up to √(s. NN)=200 Ge. V. v Has collided pp, d+Au, Au+Au and Cu+Cu. v Four heavy ion experiments STAR, PHENIX, PHOBOS, and BRAHMS Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 4 / 100 February 28 2008

STAR x θ z v Solenoidal Tracker At RHIC v v Large Experiment Many subdetectors η=-ln(tan(θ/2)) • Primary tracking sub-detector is the Time Projection Chamber which provides tracking and particle identification through ionization energy loss. Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 5 / 100 February 28 2008

Heavy Ion Collisions v In relativistic heavy ion collisions two nuclei are collided at relativistic speeds, v=0. 99 c. v The nuclei are Lorentz contracted resulting in a large amount on energy deposited in a small area. Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 6 / 100 February 28 2008

Why Use Jets ? What is a jet? Jets are the result of 2 body parton-parton hard scattering. We observed jets as cones shapes hadrons in the detector v Jets are expected to be modified by the medium we create. v We can therefore use jets to probe the medium. Side View Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago End View 7 / 100 February 28 2008

Motivation Baryon enhancement Greatly enhanced baryon over meson ratio in central Au+Au relative to pp at intermediate momentum range. Ø One of the possible scenarios is describe by coalescence model. Ø Identified trigger particle jets can give insight into this puzzle. Ø gluon jets produce more baryons than quark jets Ø Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 8 / 100 February 28 2008

PID in the TPC In this intermediate p. T region all PID bands merge together. Use relativistic rise to statistically separate particles. 1. For a selected p. T range, the d. E/dx vs p. T distribution is projected on the d. E/dx axis. A constant is used to separate positive and negative particles. 2. The measured K/p ratio is used to estimate the Kaon contribution; a 3 -gaus fit is performed with K fixed. Physics Fest at UIC 3. Getting positions from d. E/dx calibration. 4. Fixing the width to be the same and fixing the centroid positions to extract the yields for all the particles. Maria Cristina Suarez University of Illinois at Chicago STAR Preliminary 9 / 100 February 28 2008

Di- Hadron Correlation p+p Au+Au Cone |D | < 0. 5 |Dh| < 0. 5 Ridge |D | < 0. 5 |Dh| > 0. 5 Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 10 / 100 February 28 2008

Corrections • Efficiency -> we only get a % of the particles so we have to correct for the ones missing. p • Phi acceptance -> For instance there are gaps between sections of the detector, (sector boundaries) so we have to correct as a function of the angle. • Correction for detector acceptance as a function of Dh is done. Red shows the acceptance of the detector, in the cone side. Acceptance for the ridge is inverse of the cone acceptance. h • V 2 contribution Measurement of azimuthal anisotropy relative to reaction plane Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 11 / 100 February 28 2008

• Background Subtraction Contribution of the background is calculated as a function of PT associated. The higher the PT, background becomes smaller. 10% 90% STAR Preliminary D Physics Fest at UIC D Maria Cristina Suarez University of Illinois at Chicago 12 / 100 February 28 2008

Baryon Meson Background subtracted Cone STAR Preliminary Physics Fest at UIC Ridge STAR Preliminary Maria Cristina Suarez University of Illinois at Chicago 13 / 100 February 28 2008

Summary Cone: In the jet cone Baryon production is significantly lower compare to inclusive ratio measurements. Ridge: B/M production is significantly different from that in jets. B/M enhancement similar to the inclusive ratios, with an indications of additional excess of baryon yield at intermediate p. T. Thanks ! Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 14 / 100 February 28 2008

B/M partonic sources vwhy do we look at identified particles? at high-p. T affords insight into gluon and quark jet production vgluon jets produce more baryons than quark jets va probe relative energy loss for quark and gluon jets. expected, but not seen Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 15 / 100 February 28 2008

Back Up Slides Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 16 / 100 February 28 2008

Tracking Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 17 / 100 February 28 2008

Baryon Meson raw ratios Cone STAR Preliminary v v Ridge STAR Preliminary Trigger cuts: p. Ttrig > 4. 0 Ge. V/c, |htrig | < 1. 0 Associate cuts: 2. 0 Ge. V/c < p. Ttrig Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 18 / 100 February 28 2008

Au+Au 20 -30% cone away ridge Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 19 / 100 February 28 2008

V 2 contribution Measurement of azimuthal anisotropy relative to reaction plane STAR PRC C 66 034904, 2002 Betty Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 20 / 100 February 28 2008

Data set & analysis cuts Run 4, 200 Ge. V Au+Au , central triggers Trigger cuts: p. Ttrig > 4. 0 Ge. V/c, |htrig| < 1. 0 Associate cuts: 2. 0 Ge. V/c < p. Ttrig PID cut: |hassoc| < 0. 5 Cone/ridge trigger selection |htrig| < 0. 5 / |htrig| > 0. 5 Track quality: dca <1. 0 cm, fit. Pts>20 Physics Fest at UIC Maria Cristina Suarez University of Illinois at Chicago 21 / 100 February 28 2008