Noritsugu Nakatsuka 中塚 徳継 中塚徳継 1 A little bit about LHCb What is LHCb -‐It’s a detector system at p-‐p collision point focused CP violation on heavy quarks. -‐Not as famous as ATLAS and CMS, but capable of very interesting physics. 中塚徳継 2 A little bit about my supervisors My supervisors -‐Paula Collins LHCb VELO group -‐Kazuyoshi Akiba -‐Heinrich Schindler My project -‐To help testbeam time -‐Analysis on “X” project 中塚徳継 3 What is CEP? CEP=Central Exclusive Production P-P scattering produces a particle ‒NOT collision Image from [hep-‐ph:arXiv:1204:4803] 中塚徳継 4 The Problem is … We have to modify the trigger to focus on CEP events, Especially for D mesons. -It was done during the Technical Stop. My job is … -To measure the efficiency of new trigger -To compare the new trigger with the previous one The Key quantity is … -The production rate of each particles Rate= produced particles/integrated luminosity[pbarn-1] 中塚徳継 5 Test of New Trigger D0 from CEP events Events/2Mev/c2 Compare production rate of D0 per picobarn-1 Previous Trigger 0.805 0.157/pb-1 600 Luminosity = NSignal = m0 = σGauss = 580 560 LHCb Preliminary R13a 540 520 485.58 391 1866 4.44 ± 76 ± 1 MeV ± 0.69 MeV 500 480 460 440 420 Events/2Mev/c2 400 22000 Luminosity = NSignal = m0 = σGauss = 21000 20000 19000 1800 LHCb Preliminary R13c 1850 289.48 7.41e+03 ± 89 1866.7 ± 0.46 MeV 5.51 ± 0.35 MeV 1900 D0Mass(MeV/c2) Fit with Gauss +1st Chebychev 18000 New Trigger 25.6 0.31/pb-1 17000 16000 15000 1800 1850 1900 2 D0Mass(MeV/c 中塚徳継 ) 6 Results in a table Normalized Production Rate to R13a R12 D0 2011 Dplus Dstar J/Psi Phi2S 1.22 ± 0.164 1.49 ± 0.245 0.932 ± 0.082 1.19 ± 0.004 1.12 ± 0.031 Normalized Rate R13 D0 2012 Dplus Dstar 1.60 ± 0.589 1.47 ± 0.755 0.831 ± 0.271 Normalized Rate ←Relatively better results, Probably because of RICH callibration R13a D0 1 ± 0.195 2012 Dplus 1 ± 0.267 Dstar 1 ± 0.125 J/Psi 1 ± 0.004 Phi2S 1 ± 0.055 -----------Techinical Stop & Introduction of New Trigger------------------------------------Normalized Rate ←Normalized to this data R13c 2012 Data with New Trigger D0 Dplus Dstar J/Psi Phi2S 31.8 33.6 12.6 0.970 1.05 ± ± ± ± ± 0.39 5.34 0.61 0.005 0.063 ←Huge effects on D mesons ←Muon channels stay the same 中塚徳継 7 Search for X(3872) What is X(3872)? -‐It’s a particle found at Belle in Japan first. -‐It’s now on ccbar section on PDG. Belle Nobody knows what “X” truly is. Even quantum numbers are yet to be measured. -‐Some predictions say it’s a molecular state of DD. How we search the particle? -‐“Invariant Mass Spectroscopy” in CEP events -‐Measuring the energy and momentum of daughter particles and reconstruct the invariant mass of the parental particle 中塚徳継 8 Decay Mode of X Check the PDG. ‒the bible of particle physicists X(3827) -> π+π-J/ψ (>2.6%) ←Let s begin with this one -> ωJ/ψ (>1.9%) ->…other minor decays ->… J/ψ -> μ+ μ- ( 5%) ← Let s begin with this -> e+ e- ( 5%) 中塚徳継 9 Let’s take a look. Events/2Mev/c2 X -> π+π- J/ψ reconstructed data. 240 220 200 180 160 140 120 100 80 60 40 20 0 Luminosity = NSignal core = m0 core = σGauss core = NSignal X = m0 X = σGauss X = LHCb Preliminary R12,R13 R13a,R13c 2 gauss 3600 1938.2 2.75e+03 3711.5 7.79 86.3 3882.8 14.4 ± 77 ± 2.4e+02 MeV ± 6.3 MeV ± 76 ± 21 MeV ± 15 MeV 1 gauss Fit with 3 gauss + 5th order chebychev 3800 4000 X mass (MeV/c2) ↑ This is a peak from ψ’. (Width=7.79MeV) -Perfect reference to optimize the fit&cut 中塚徳継 10 Search for better cut conditions Events/4Mev/c2 -Using ψ peak width as reference. -The best results came from M(J/ψπ+π-)-M(J/ψ) with J/ψ Mass Constraint plot. Width=2.67MeV 300 250 200 LHCb Clear Preliminary R12,R13 R13a,R13c X signal ! Luminosity = NSignal core = m0 core = σGauss core = NSignal X = m0 X = σGauss X = 1938.2 2.75e+03 589.63 2.67 104 775.83 2.5 ± 69 ± 0.081 MeV ± 0.12 MeV ± 25 ± 0.64 MeV ± 0.87 MeV 150 100 50 2 gauss 0 400 1 gauss 600 800 Fit with 3 gauss + 5th order chebychev 中塚徳継 1000 1200 X mass (MeV/c2) 11 Thanks a lot to all of you! 中塚徳継 12
© Copyright 2024 ExpyDoc
