Presentation on theme: "Design and Testing of a Quartz Plate Cherenkov Calorimeter Prototype & Search for a Right Handed Majorana Mass Neutrino Using the CMS Detector Warren Clarida."— Presentation transcript:
Design and Testing of a Quartz Plate Cherenkov Calorimeter Prototype & Search for a Right Handed Majorana Mass Neutrino Using the CMS Detector Warren Clarida
Outline W. Clarida 2 Introduction to the Large Hadron Collider (LHC) and Compact Muon Solenoid (CMS) Detector Design and Testing of the 1 st Phase Quartz Plate Calorimeter (QPC) Prototype - Motivation of design - Test Beam Results Heavy Majorana Mass Neutrino Search with the CMS Detector at the (LHC) - Introduction - Monte Carlo Studies - Backgrounds - 2010 Data Results - Still To Be Done
W. Clarida 3 IP1- ATLAS (general purpose) IP5-CMS (general purpose) IP2-ALICE (Heavy Ion, p-ion) IP8-LHCb (pp B-Physics) Design: 2808x2 bunches protons, 10 11 protons/bunch, 14 TeV center of mass energy 2011: 7 TeV center of mass energy, 930/1400 bunches > 10 33 cm -2 s -1 - Expect more than 1 fb -1 Large Hadron Collider
Why Quartz Cerenkov Calorimeter W. Clarida 5 Increasing beam energy and luminosities brings increased radiation levels in HEP detectors. Conventional calorimeters relying upon scintillating materials that are not sufficiently rad hard in these new types of environments. This problem was solved for the forward region of the CMS detector by a Cerenkov detection based Hadronic Forward Calorimter (HF) This experience lead to the design of a sampling Cerenkov Quartz Calorimeter Prototype.
Motivation Coming From The (S)LHC Time-line ~2021/22 2017 or 18 2013/14 2009 Start of LHC Run 1: 7 TeV centre of mass energy, luminosity ramping up to few 10 33 cm -2 s -1, few fb -1 delivered 2030 ILC, High energy LHC,... ? Phase-II: High-luminosity LHC. New focussing magnets and CRAB cavities for very high luminosity with levelling Injector and LHC Phase-I upgrades to go to ultimate luminosity ~5x10 34 LHC shut-down to prepare machine for design energy and nominal luminosity Run 4: Collect data until > 3000 fb -1 Run 3: Ramp up luminosity to 2.2 x nominal, reaching ~100 fb -1 / year accumulate few hundred fb -1 Run 2: Ramp up luminosity to nominal (10 34 cm -2 s -1 ), ~50 to 100 fb -1 From T1.00002: The LHC and Beyond April 2011 APS Radiation Increase
SLHC -> CMS Calorimeter Upgrade W. Clarida, DPF 2009 8 Quartz plates will not be affected by high radiation. Quartz in the form of fiber was irradiated in Argonne IPNS for 313 hours. The fibers were tested for optical degradation before and after 17.6 Mrad of neutron and 73.5 Mrad of gamma radiation. Quartz plates could be used to replace plastic scintillators. Current HE not sufficiently radiation hard Plastic scintillator tiles and wavelength shifting fiber is radiation hard up to 2.5 MRad while at SLHC, expect 25MRad in HE. R&D new scintillators and waveshifters in liquids, paints, and solids, and Cerenkov radiation emitting materials e.g. Quartz Current HE not sufficiently radiation hard Plastic scintillator tiles and wavelength shifting fiber is radiation hard up to 2.5 MRad while at SLHC, expect 25MRad in HE. R&D new scintillators and waveshifters in liquids, paints, and solids, and Cerenkov radiation emitting materials e.g. Quartz
Quartz Plate Prototype I W. Clarida A single tower calorimeter prototype was simulated and developed for testing. - Quartz plates with imbedded fibers were layered between iron blocks. 9
2006 Test Beam W. Clarida 10 The QPC1 was test at both Fermilabs meson test beam facility and CERNs H2 beam line facility. Energy scans and surface scans were done at both locations. Both electromagnetic and hadronic responses were tested. The uniformity of response by QPC1 for 100 GeV electrons.
Hadronic Calorimeter Setup Hadronic setup mimicked HE with 5cm steel absorber between each layer. 20 layers were read out. Proof of concept but light yield not sufficient for HE needs. W. Clarida 11 Hadronic ResolutionHadronic Response Linearity
Electromagnetic Setup With the absorber depth reduced to 2cm the QPC1 can act as an Ecal. We wee a Cerenkov calorimeter is a radiation hard option for future calorimeters at high energy high radiation detectors. Light yield probably needs to be increased. - Future QPC prototypes with the use of scintillating coatings on plates. W. Clarida 12 Electromagnetic Resolution
Introduction To Majorana Neutrinos We know that neutrinos must be massive particles. 1.9 × 103 eV 2 < m 2 atm < 3.0 × 103 eV 2 7 × 105 eV 2 < m 2 sol < 9 × 105 eV 2 The simplest method of adding a Dirac mass term in the SM requires right handed neutrinos, which havent been observed. With the addition of Majorana mass terms 1 the left handed nature of the 3 known neutrinos can be preserved. They would have a mass scale given so called seesaw relationship: m M m ν ~ m D 2 where the Majorana mass and neutrino mass must balance each other and the dirac mass is on the order of a standard quark or lepton mass. There would be an addition of new heavy Majorana mass neutrinos with a mass m N ~ m M We are searching for such a massive neutrino at the LHC. There have been two recent papers which discuss the potential of finding a heavy Neutrino between the masses of 100 and 200 GeV at the LHC - The Search for Heavy Majorana Neutrinos 1 - The Little Review on Leptongenesis 2 W. Clarida 14 1) A. Atre, T. Han, S. Pascoli, B. Shang, 0901.3589 [hep-ph] 2) A. Pilaftsis, 0904.1182 [hep-ph]
Signature The Majorana nature of the heavy neutrino allows for lepton number violating final states. - In order to still be within the SM, we only look at decays with SM gauge bosons. - Our primary signature is chosen to be two same sign muons with no E T miss and 2 jets from a W. We will look first for decay into muons - non-observation of neutrinoless double- β decay puts a very low bound on the mixing element for electrons: - Also this takes advantage of the excellent muon detection of CMS. W. Clarida 15
CMS Muon Reconstruction 16 Muon are reconstructed combining information from the central tracker and the muon system. Achieving a momentum resolution of ~3% for muon p T < 300 GeV. Charge mis-ID for this range is ~ 10 -5 The acceptance region is:
Current Limits & CMS Contribution W. Clarida 17 In 2009, the mass range of 100 GeV – 200 GeV was studied, there are no current limits set from direct searches. The full mass range was expected to be excluded with 100 pb -1 at 10 TeV. (S μμ =1 & S μμ V N μ ). For our search we use a parameterization of the cross section. The equation relating the S value and the cross section is below. The other parameter, σ 0 (N 4 ), is the bare cross section depending only upon the neutrino mass and the collision energy. 1) arXiv:0901.3589v2
W. Clarida 18 7TeV Signal Generation A program based upon matrix element calculation is used to generate weighted Majorana neutrino events with pp collision properties. (written by T. Han U. Wisconsin) The output from the first step is is in unweighted Les Houches format. These events are interfaced with CMSSW to include parton showering with pythia. Full detector Simulation, digitization and reconstruction are then performed. We produced datasets for the masses: 50, 60, 70, 80, 90, 100, 110, and 120 GeV. Mass30405060708090100110120 σ 0 (N 4 ) (pb) 98.4122.1135.0114.869.620.06.03.01.30.8
W. Clarida 19 Muon Distribution At low mass the muon pt distribution is split. As the neutrino mass increases the muon pt distributions converges and then begins to increase. The eta and phi distributions are all flat across the mass range.
Muon Isolation The Ecal and Hcal isolation is the sum of deposits within an dR cone of 0.3. The relative isolation is the sum of the deposits/max(20, mu pt) All three of the isolations distributions we use dont change as the neutrino mass increases.
JetMET W. Clarida 21 MET, Jet Multiplicity and Jet Pt all increase with Majorana Mass
2 nd Jet/Muon Pt Cuts Our event signature is 2 jets + 2 muons, however at the lower masses the 2 nd objects can be difficult to identify. Our efficiency when requiring two jets is very low for the much of the studied mass range. We use asymmetrical cuts for the muon pt so this effect isnt as significant. W. Clarida 22
Selection Cuts Muons - Mu pt > 20, 10 (1 st muon, 2 nd muon) - Eta < 2.4 - Ecal Isolation < 4 GeV - Hcal Isolation < 6 GeV - Relative Isolation < 0.1 - Normalized Chi 2 < 10 - D 0 < 0.2 mm - 11 hits in tracker, at least one muon system hit - Global and tracker Muon - Dimuon mass > 5 GeV - No event with 3 rd muon in Z mass window Jets - 2 Jets with pt > 20 GeV, eta < 3.0 W. Clarida 23 Quality Cuts Isolation Cuts Pt Cuts Z veto
Backgrounds W. Clarida 24 Real backgrounds WW, WZ, ZZ, tW - These are backgrounds than can produce 2 same sign muons. - Take contribution from Monte Carlo. Fake backgrounds QCD, tt, W+jets - Processes where one or both muons are faked from jets. - Used loose/tight method to get muon fake rate from data - Closure check with ttbar and QCD MC. Assign systematic.
Real Backgrounds For the 2010 date the contributions from the real backgrounds are insignificant. We also considered Z/ γ +Jets. The contribution from this background was negligible. W. Clarida 25 σ (pb) Yield (34 pb -1 ) Error (stat) # MC events WZ10.50.0420.003254 WW280.001 2 ZZ4.30.0090.001124 tW10.560.0150.00320 Total0.0670.004
Muon Fake Rate Determination W. Clarida 28 To estimate the number of events we should expect from fake muons we determine the fake rate using a loose/tight method. The rate is a ratio of the number of muons passing a set of tight and loose cuts. Events with a fakeable object are weighted by a factor determined by the fake rate (f) of f/(1-f) - N exp = N w/ttbar + N QCD - N w/ttbar is obtained from the number events with one loose muon not passing the tight cuts - N QCD is obtained from the number of events with two loose muons not passing the tight cuts. - N w/ttbar must be corrected for double counting events where there are two fakes but one pass the full selection criteria - Currently there is no correction for signal contamination as we see no excess. The f is a function of muon p T and η.
Muon Fake Rate Cuts W. Clarida 29 We look for events with a well separated opposite side jet. Δ R>1.0 from the muon. Fake rate dependence on jet p T. - Prediction from 40 GeV cut compared to actual results for 20,40,60 GeV cuts in QCD MC. - There is an over prediction for events with high p T jets - Accounted for in our final systematics. Muons: - p T > 10 GeV - η < 2.4 - RelIso < 0.1 (0.4 for loose) - Χ 2 /ndof < 10 - Transvers IP < 0.2 mm Jets: - p T > 40 GeV - η < 3.0 Trigger - HLT_Mu9
T/L Ratio W. Clarida 30 | η |/P T 10-1515-2020-2530-35 0.0-1.00.19620.00520.13310.00920.13270.01470.11070.0134 1.0-1.4790.22920.00870.15900.01460.09760.01720.09030.0169 1.479-2.00.23640.00890.14310.01380.12660.01890.12230.0181 2.0-2.50.25870.01570.16890.02500.08420.02850.07830.0250 Single Fake Prediction: - 3.089 ± 0.247 events (N s ) Double Fake Prediction: - 2.082 ± 0.323 events (N D ) Total Fake Prediction - 1.007 ± 0.735 (N F ) Wait 3+1 1 - The single prediction over counts by including double fake events where one muon passed the tight criteria. - N F = N S - N D
Closure Test & Systematic Error W. Clarida 31 Predict the dimuon rate in ttbar with FR obtained from QCD MC In the ttbar sample we find 63 fake muons. The FR prediction is 104.79 ± 3.79 This gives us a ratio of predicted/observed 1.66 The over prediction seems to come from a high jet P T tail present in ttbar, not in QCD. This leads us to assign a 50% systematic error on our fake rate result.
95% Preliminary Exclusion 2010 W. Clarida 32 This is preliminary. It does not contain all systematic errors. Much of the 2011 sensitive mass region has not been studied. 2010 results above 100 GeV are not competitive with precision electroweak measurements. Already 7 times more data in 2011.
To Be Done W. Clarida 33 Redo Analysis with 2011 Data - Understand pile up Understand Trigger efficiencies for signal - Not in current MC Include systematics in exclusion result - JES and muon reconstruction not expected to have significant affect – must confirm. - Use Alpgen (another generator) to understand systematics from signal MC - Include pile up systematics - Systematic on expected real backgrounds Extend search up to ~200 GeV Investigate use of MET significance cut.
Fake Rate Calc. Details W. Clarida 35 Define some variables: - f: ratio of muons passing tight cuts to those passing loose cuts - N L : Events with 2 muons passing loose cuts - N mu : Events with 2 real muons - N S : Events with 1 real and 1 fake muon - N D : Events with 2 fake muons - N 2t,1t,0t : Events where 2, 1, or 0 muons pass tight cuts N L can be written in terms of measurable N 2t,1t,0t or in terms of truth N mu,S,D - N L = N mu + N S + N D = N 2t + N 1t + N 0t The measurable can be written in terms of the truth - N 0t = (1-f) 2 N D - N 1t = (1-f)N S + 2f(1-f)N D - N 2t = N mu + fN S + f 2 N D Work out the algebra and get: - N 2t = N mu + f/(1-f)N 1t – 2f 2 /(1-f) 2 N 0t + f 2 /(1-f) 2 N 0t
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