Subtracting Combinatorial Background in μ+μ- Spectra Using μ+μ+ and μ-μ- Pairs or Recombination Method: Hypotheses, Adva
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This study explores the application of μ+μ+ and μ-μ- pairs or a recombination method to subtract combinatorial background in μ+μ- spectra. Investigating hypotheses, advantages, disadvantages, and analyzing real data and simulations. It examines the necessary steps to validate this method and discusses experimental constraints, advantages, and difficulties associated with the approach.
Subtracting Combinatorial Background in μ+μ- Spectra Using μ+μ+ and μ-μ- Pairs or Recombination Method: Hypotheses, Adva
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Subtracting combinatorial background in μ+μ- spectra Using μ+μ+ and μ-μ- pairs or a recombination method (mixing event) Hypothesizes, advantages, disadvantages… Real data and simulation (first attempt) What must be done to check that we can use the method using μ+μ+ and μ-μ- pairs.
Using μ+μ+ and μ-μ- pairs • Hypothesizes: H1: Muons from a pair are not physically correlated H2: No correlation between meson + and – multiplicities H3: Multiplicities follow a Poisson distribution • Experimental constraint: Accμ+μ-(M0) = Accμ+μ+(M0) = Accμ-μ-(M0) Nμ+μ+ / Nμ-μ- • Nμ+μ-(Bgr) = 2 (Nμ+μ+ Nμ-μ-)½ ≈ Nμ+μ+ + Nμ-μ- Nμ+μ-(Sgl) = Nμ+μ- - Nμ+μ-(Bgr) for A-A
Using μ+μ+ and μ-μ- pairs in p-p, p-A… Small multiplicities H2 (no correlation between mesons + and mesons -) not right: Nμ+μ-(Bgr) = 2 R (Nμ+μ+ Nμ-μ-)½, R>1 R estimated using MC simulation
Recombination method • Hypothesis:muon kinematical distributions from pairs identical with distributions if measure muons individually • Condition:combination between muons from same Δzvertex and Δb class of events • Advantages: - high statistics - do not need Accμ+ = Accμ- • Difficulties: - Bias introduced by cuts - Uncertainty calculation
Au-Au mass spectra no ghost Real Data (runs 28284+28286+ 28302 Sept 17th-18th) Simulation: Central + J/ψ (MDC) (49300 evts) ZDCNS*BBCLL1≥2
Au-Au mass spectra no ghost Real Data (runs 28284+28286+ 28302 Sept 17th-18th) Simulation: Central + J/ψ (MDC) (49300 evts) ZDCNS*BBCLL1≥2
Au-Au pT and y spectra Real Data (runs 28284+28286+ 28302 Sept 17th-18th) ZDCNS*BBCLL1≥2
What must be done • Check if Accμ+μ-(X) = Accμ+μ+(X) = Accμ-μ-(X), (X=M, pT, y…) and/or Accμ+= Accμ+ ▪ simulations: - with a perfect detector - introducing dead channels: 1) FEM 2) HV ▪ real data: - study Nμ+μ+/Nμ-μ- versus M, pT, y • See which cuts applying • Understand why 2*(Nμ+μ+ Nμ-μ-)½ > Nμ+μ- at low masses • Check if the value of Nμ+μ+/Nμ-μ- is reproduced by the simulation
References Recombination methods in PHENIX central arms – e’s: • Y. Akiba: https://www.phenix.bnl.gov:8080/phenix/WWW/p/draft/akiba/01.01/ AN_PART2.pdf • F. Matathias: http://www.phenix.bnl.gov/phenix/WWW/p/lists/phenix-heavy-l/recent/msg00240.html Recombination method and R calculation in NA38/NA50: • “Etude de la production du J/ψ dans les réactions p-Cu, p-U, O-U et S-U à 200 GeV par nucléon” PhD thesis S. Papillon, Paris-7 university (March 1991), IPNO-T.91.03 • “Estimation of the combinatorial background in dimuon spectra using recombination of muons, and associated error” S. Constantinescu, S. Dita, D. Jouan (1996), IPNO-DRE-96-01 • “Intermediate mass dimuons in ultrarelativistic proton-nucleus and nucleus-nucleus collisions at the CERN-SPS” PhD thesis Cristina Soave, Tesi di Dottorato di Ricerca, Università Degli Studi Di Torino, April 1998. (see chapter 5) http://na50.web.cern.ch/NA50/theses.html Limit of the methods estimating the combinatorial background: • M. Gaździcki and M. I. Gorenstein hep-ph/0003319 Combinatorial background in ALICE: • P. Crochet and P. Braun-Munzinger nucl-ex/0106008
