TheZ resonance is described by a Breit-Wigner distribution if no detector effects are taken into account. On the other hand, the experimental resolution of the energy (1/pT) measurement on the electrons (muons) is approximately described by a Gaussian distribution. To account for this, the Z resonance is fitted by a convolution of the Breit-Wigner and the Gauss functions in the evaluation of the performance of the mass methods. For the case that the Z decays to τ leptons, the τ reconstruction effects are dominating and hence, the Z resonance is better described by a Gaussian distribution than by a Breit-Wigner. Nonetheless, a Gaussian and a Breit-Wigner function are fitted to the data and the signal Monte Carlo for all the mass methods after all relevant cuts have been applied. The data are fitted after subtracting the background
132
(a)meff electron channel (b) meff muon channel
(c) mcollelectron channel (d) mcollmuon channel
(e) MMC electron channel (f) MMC muon channel
Figure 9.6: Mass distributions of theτ τ system forτeτh (left) andτµτh (right). The distribu-tions are plotted after all standard cuts includingETmiss>20 GeV.
(a) mboundelectron channel (b) mboundmuon channel
(c)mtrueT electron channel (d) mtrueT muon channel
(e)mbound ormtrueT electron channel (f) mboundormtrueT muon channel
Figure 9.7: Mass distributions of theτ τ system forτeτh (left) andτµτh (right). The distribu-tions are plotted after all standard cuts includingETmiss>20 GeV.
134
(a) electron channel (b) muon channel
Figure 9.8: Collinear approximation forτeτh(left) andτµτh(right). The distribution is plotted after all standard cuts includingETmiss >20 GeV and |∆φ(τ,lepton)|<2.9.
contribution from the Monte Carlo predictions. The resulting curves are shown in Fig. 9.9 and 9.10 and mean values and widths are summarised in Tables 9.1 and 9.2.
To check the stability of the methods, the masses are reconstructed after varying the domi-nant systematic uncertainty of the process, the energy scale, and the deviation from the nominal value is given in Table 9.3. For the MMC two extra systematic uncertainties are checked, the ETmiss and the jet energy resolution. The corresponding effects are presented in Table 9.4. The systematic uncertainties are discussed previously for each method separately.
A final check of the performance of the methods is done by estimating the ratio of the signal over the background contributions, which is summarised in Table 9.5. The muon channel has a higher background rejection efficiency due to the stronger suppression of theZ+jets background.
Amongst the studied methods, the ones that constrain the phase space using theτ decay topol-ogy, like the MMC and the mbound methods, provide a better separation between signal and background. However, the collinear approximation offers comparable separation power without using statistical methods that might introduce additional systematic uncertainties.
(a) signal data – electron channel (b) signal MC – electron channel (c) signal data – electron channel
(d) signal MC – electron channel (e) signal data – electron channel (f) signal MC – electron channel
(g) signal data – electron channel (h) signal MC – electron channel (i) signal data – electron channel
(j) signal MC – electron channel (k) signal data – electron channel (l) signal MC – electron channel
Figure 9.9: Fit all mass distribution for the τeτh channel after the necessary cuts have been applied, for signal Monte Carlo (right) and data after subtracting the background expectation from Monte Carlo (left).
136
(a) signal data – muon channel (b) signal MC – muon channel (c) signal data – muon channel
(d) signal MC – muon channel (e) signal data – muon channel (f) signal MC – muon channel
(g) signal data – muon channel (h) signal MC – muon channel (i) signal data – muon channel
(j) signal MC – muon channel (k) signal data – muon channel (l) signal MC – muon channel
Figure 9.10: Fit of mass distribution for the τµτh channel after the necessary cuts have been applied.
Table 9.1: The Gaussian (g) and Breit Wigner (BW) mean and width values of the
Table 9.2: The Gaussian and Breit Wigner (BW) mean and width values of the reconstructed masses for data.
Table 9.3: The shift of the mean and width of the Gauss fit function for the different masses
Table 9.4: The shift of the mean and width for the Gauss fit functions for MMC when the ETmiss resolution (METr) and the jet energy resolution (JER) are varied.
mMMC [τeτh] µ [GeV] σ [GeV]
Table 9.5: Signal over background efficiency of the mass methods.
τeτh s/bg
Chapter 10
Conclusions
In this thesis, the measurement of the semi-leptonicZ →τ τ decay was presented with the data collected in 2010 and 2011 by ATLAS. The latter set of data was also used to study τ τ mass reconstruction methods.
Studying and understanding the Z →τ τ signal and, as a matter of fact, allZ andW boson decays is a pre-requisite for any searches for the Higgs boson or new physics. That is because the properties and the decays of the Z and the W bosons are known to a great accuracy and can serve as calibration tools for the data and the methods used. Especially, for Higgs boson searches, theZ →τ τ process is an irreducible background lying in the same mass range that a light Higgs boson is expected. Hence, before claiming discovery or exclusion of the latter, it is necessary to prove that the former is well-modelled.
The first step is the measurement of the cross section of the process. For that the semi-leptonic decays were used, where oneτ lepton decays to pions and the other to either electrons or muons. The main background contribution comes from the QCD multijets, the suppression of which is achieved with an isolation requirement on the electrons and muons. Moreover, the remaining events are modelled with a two-dimensional template fit, called ABCD method.
Further kinematical and identification requirements have been implemented to suppress the electroweak background events.
The final measured inclusive cross section when taking into account the branching fraction of the τ leptons to pions and electrons or muons is:
• with the data collected in 2010:
σ(Z →τ τ, minv : [66−116] GeV) = 857.6±84.3(stat)±124.7(syst)±29.2(lumi)±2.8(theo) pb (10.1) for theτµτh channel,
σ(Z →τ τ, minv : [66−116] GeV) = 1142±138.6(stat)±197.7(syst)±38.9(lumi)±2.6(theo) pb (10.2) for theτeτh channel.
• with the data collected in 2011:
σ(Z →τ τ, minv : [66−116] GeV) = 912.4±15.0(stat)±94.7(syst)±33.7(lumi) pb (10.3) for theτµτh channel,
σ(Z →τ τ, minv: [66−116] GeV) = 998.1±23.7(stat)±131.9(syst)±36.9(lumi) pb (10.4) for theτeτh channel.
The measurements agree within uncertainties with the theoretical NNLO expectation value, 960
±50 pb−1.
After having established the selection criteria and methods for theZ →τ τ decay, the process is used to evaluate the most prominent reconstruction methods for theτ τ system. These meth-ods are: effective mass, collinear approximation, missing mass calculator, bound mass, “true”
transverse mass and the combination of the last two. The effective and the “true” transverse mass, although they are reconstructing the full event, they are not utilising τ properties and hence, do not constrain the event. Nonetheless, they are able to reconstruct the Z resonance with 100% efficiency. Therefore, they can be useful if one is limited by statistics but has a good knowledge of the background processes. The opposite is true for the collinear approximation and the bound mass, in which case, 40-50% of the events are rejected from the phase-space con-straints of the methods, but a good signal over background separation is possible. The combined method seems to overcome the disadvantages of the two separate methods, but, nonetheless, it inherits some of the disadvantages, more notably, the events reconstructed with the “true” trans-verse mass suffer from low background rejection. Finally, the missing mass calculator constrains the τ τ system in almost 95% of the phase-space and thanks to the likelihood method it uses, it succeeds in providing good signal to background separation. One drawback is the sensitivity of the method on the mis-measurements of the angular coordinates between the visible decay products and the missing transverse momentum. Additionally, due to the need for initial tuning of the discriminant, the method is not flexible to any changes in the event selection.
To summarise, a first measurement of the Z → τ τ cross section was done with the data collected in 2010, which was then improved by the measurement in the data collected in 2011.
The latter were used to further reconstruct the invariant mass of the τ τ system and evaluate different methods. Further improvements are always possible, specially the better understanding of the detector and the tools is acquired. A larger statistical sample is not necessary for the cross section measurement, rather a better estimation of the energy scale uncertainties is necessary. In contrast, the reconstruction of the full invariant mass still suffers from statistics, so an extension of the studies to the full 2011 dataset would be beneficial. Then, it would also be possible to study and evaluate the uncertainties on the background events and hence, more concrete conclusions could be drawn on the discovery power of the methods. Nonetheless, the methods and selection criteria developed have already been used for the evaluation of systematic uncertainties on the identification and reconstruction of the hadronicτ candidates in tag-and-probe studies in data.
Also, in Higgs boson searches in theτ τ decay mode, several of the studied methods are already used and the others are currently under consideration.
142
Appendix A
Monte Carlo Samples
All simulated samples used in this study are listed in Table A.1 for 2010 and Tables A.2, A.3, A.4 and A.5 for 2011. In the tables are given the number of generated events, the particular dataset number and reference tags (AMI tag) for the specific ATLAS reconstruction campaign.
Additionally, the NNLO cross sections and the K-factors, where applied, are listed.
TableA.1:ListofMonteCarlosamplesusedforthisanalysis.AllsamplesweregeneratedwithPYTHIA,exceptfort¯twhichwasgeneratedwithMC@NLOandthedibosonsamplesgeneratedwithHERWIG.
DatasetDatasetNumberAMITagEventsCross-Section/pbZ→ee(m``>60GeV)106046e574s933s946r1831r20405M990Z→µµ(m``>60GeV)106047e574s933s946r1831r20405M990Z→ττ(m``>60GeV)106052e574s934s946r1833r20402M990W→eν106043e574s933s946r1831r20407M1046W→µν106044e574s933s946r1831r20407M1046W→τν107054e574s934s946r1833r17002M1046t¯t105200e598s933s946r1831r17001M91.50J1e(electronfilterpT>8GeV,|η|<3)109271e600s934s946r1833r1700998k8.81×10 5
J2e(electronfilterpT>8GeV,|η|<3)109272e574s934s946r1833r1700497k2.54×10 5
J3e(electronfilterpT>8GeV,|η|<3)109273e574s934s946r1833r1700499k3.72×10 4
J0mu(muonfilterpT>8GeV,|η|<3)109276e574s933s946r1831r1700967k8.48×10 5
J1mu(muonfilterpT>8GeV,|η|<3)109277e574s933s946r1831r1700997k8.14×10 5
J2mu(muonfilterpT>8GeV,|η|<3)109278e574s933s946r1831r1700495k2.21×10 5
J3mu(muonfilterpT>8GeV,|η|<3)109279e574s933s946r1831r1700499k2.85×10 4
γ ∗/Z→ττ(10GeV<m``<60GeV)107055e574s933s946r1831r2040190k396.7γ ∗/Z→ee(15GeV<m``<60GeV)108320e574s933s946r1831r1700996k146.2γ ∗/Z→µµ(15GeV<m``<60GeV)108319e574s933s946r1831r1700999k146.2WW105985e598s933s946r1831r2040250k11ZZ105986e598s933s946r1831r2040250k1.0WZ105987e598s933s946r1831r2040250k3.4
144
TableA.2:ListofMonteCarlosamplesfortheZ+jetsproduction.ThesamplesaregeneratedwithAlpGENandaresplitpernumber ofinitialpartons(NpX,X=0,...,5).AminimumpartonpTcutat20GeVisappliedatproduction. ProcessDatasetNumberAMITagLOCrossSection*NNLO-factor[pb]Events Z→ττ(m``>40GeV)+Np0107670e844s933s946r2302r2300668.40*1.256608784 Z→ττ(m``>40GeV)+Np1107671e844s933s946r2302r2300134.81*1.251327672 Z→ττ(m``>40GeV)+Np2107672e844s933s946r2302r230040.36*1.25403864 Z→ττ(m``>40GeV)+Np3107673e844s933s946r2302r230011.25*1.25109947 Z→ττ(m``>40GeV)+Np4107674e844s933s946r2302r23002.79*1.2529977 Z→ττ(m``>40GeV)+Np5107675e844s933s946r2302r23000.77*1.259990 Z→ee(m``>40GeV)+Np0107650e737s933s946r2302r2300668.32*1.256612265 Z→ee(m``>40GeV)+Np1107651e737s933s946r2302r2300134.36*1.251333745 Z→ee(m``>40GeV)+Np2107652e737s933s946r2302r230040.54*1.25404873 Z→ee(m``>40GeV)+Np3107653e737s933s946r2302r230011.16*1.25109942 Z→ee(m``>40GeV)+Np4107654e737s933s946r2302r23002.88*1.2529992 Z→ee(m``>40GeV)+Np5107655e737s933s946r2302r23000.83*1.258992 Z→µµ(m``>40GeV)+Np0107660e737s933s946r2302r2300668.68*1.256619010 Z→µµ(m``>40GeV)+Np1107661e737s933s946r2302r2300134.14*1.251334723 Z→µµ(m``>40GeV)+Np2107662e737s933s946r2302r230040.33*1.25403886 Z→µµ(m``>40GeV)+Np3107663e737s933s946r2302r230011.19*1.25109954 Z→µµ(m``>40GeV)+Np4107664e737s933s946r2302r23002.75*1.2529978 Z→µµ(m``>40GeV)+Np5107665e737s933s946r2302r23000.77*1.259993
TableA.3:ListofMonteCarlosamplesforW+jetsproduction.ThesamplesaregeneratedwithAlpGENandaresplitpernumberofinitialpartons(NpX,X=0,...,5).AminimumpartonpTcutat20GeVisappliedatproduction.
ProcessDatasetNumberAMITagLOCrossSection*NNLO-factor[pb]EventsW→τν+Np0107700e844s933s946r2302r23006918.60*1.203259564W→τν+Np1107701e844s933s946r2302r23001303.20*1.202496467W→τν+Np2107702e844s933s946r2302r2300378.18*1.203764804W→τν+Np3107703e844s933s946r2302r2300101.51*1.201008514W→τν+Np4107704e844s933s946r2302r230025.64*1.20248864W→τν+Np5107705e844s933s946r2302r23007.04*1.2064950W→eν+Np0107680e600s933s946r2302r23006921.60*1.203455037W→eν+Np1107681e798s933s946r2302r23001304.30*1.202499513W→eν+Np2107682e760s933s946r2302r2300378.29*1.203768265W→eν+Np3107683e760s933s946r2302r2300101.43*1.201009641W→eν+Np4107684e760s933s946r2302r230025.87*1.20249869W→eν+Np5107685e760s933s946r2302r23007.00*1.2069953W→µν+Np0107690e600s933s946r2302r23006919.60*1.203466523W→µν+Np1107691e798s933s946r2302r23001304.20*1.202499513W→µν+Np2107692e760s933s946r2302r2300377.83*1.203768893W→µν+Np3107693e760s933s946r2302r2300101.88*1.201009589W→µν+Np4107694e760s933s946r2302r230025.75*1.20254879W→µν+Np5107695e760s933s946r2302r23006.92*1.2069958
146
TableA.4:ListofMonteCarlosamplesforthelowmassZ+jetsprocess.ThesamplesaregeneratedwithAlpGENandaresplitper numberofinitialpartons(NpX,X=0,...,5).AminimumpartonpTcutat20GeVisappliedatproduction. ProcessDatasetNumberAMITagLOCrossSection*NNLO-factor[pb]Events γ∗/Z→ττ(10GeV<m``<40GeV)+Np0116270e844s933s946r2302r23003055.1*1.25959877 γ∗/Z→ττ(10GeV<m``<40GeV)+Np1116271e844s933s946r2302r230084.93*1.25296945 γ∗/Z→ττ(10GeV<m``<40GeV)+Np2116272e844s933s946r2302r230041.47*1.25498804 γ∗ /Z→ττ(10GeV<m``<40GeV)+Np3116273e844s933s946r2302r23008.36*1.25149953 γ∗ /Z→ττ(10GeV<m``<40GeV)+Np4116274e844s933s946r2302r23001.85*1.2539980 γ∗ /Z→ττ(10GeV<m``<40GeV)+Np5116275e844s933s946r2302r23000.46*1.259995 γ∗/Z→ee(10GeV<m``<40GeV)+Np0116250e660s933s946r2302r23003055.2*1.25999859 γ∗/Z→ee(10GeV<m``<40GeV)+Np1116251e660s933s946r2302r230084.92*1.25299940 γ∗/Z→ee(10GeV<m``<40GeV)+Np2116252e660s933s946r2302r230041.41*1.25499880 γ∗/Z→ee(10GeV<m``<40GeV)+Np3116253e660s933s946r2302r23008.38*1.25149940 γ∗/Z→ee(10GeV<m``<40GeV)+Np4116254e660s933s946r2302r23001.85*1.2539973 γ∗/Z→ee(10GeV<m``<40GeV)+Np5116255e660s933s946r2302r23000.46*1.259995 γ∗/Z→µµ(10GeV<m``<40GeV)+Np0116260e660s933s946r2302r23003054.9*1.25999869 γ∗/Z→µµ(10GeV<m``<40GeV)+Np1116261e660s933s946r2302r230084.87*1.25299890 γ∗/Z→µµ(10GeV<m``<40GeV)+Np2116262e660s933s946r2302r230041.45*1.25499864 γ∗/Z→µµ(10GeV<m``<40GeV)+Np3116263e660s933s946r2302r23008.38*1.25149939 γ∗/Z→µµ(10GeV<m``<40GeV)+Np4116264e660s933s946r2302r23001.85*1.2539988 γ∗/Z→µµ(10GeV<m``<40GeV)+Np5116265e660s933s946r2302r23000.46*1.259996
TableA.5:ListofMonteCarlosamplesfort¯tprocessgeneratedwithMC@NLOandfordibosonproductiongeneratedwithHERWIG.
ProcessDatasetNumberAMITagCrossSection[pb]Eventst¯t(nofullyhadronicdecays)105200e844s933s946r2302r230090.1514845714WW105985e598s933s946r2302r230017.022495756ZZ105986e598s933s946r2302r23005.54249906WZ105987e598s933s946r2302r23001.26249923
148
Bibliography
[1] J. Allday, Quarks, Leptons and the Big Bang, CRC Press, (2001), ISBN 9780750308069.
[2] The ATLAS Collaboration, G. Aad et al.,Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC, Phys.Lett.B 716(1)(2012) 1.
[3] The CMS Collaboration, S. Chatrchyan et al.,Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC, Phys.Lett.B (2012), 1207.7235.
[4] The Particle Data Group Collaboration, K. Nakamuraet al.,Review of particle physics, J.
Phys.G37 (2010) 075021.
[5] R. K. Ellis, W. J. Stirling, and B. R. Webber,QCD and Collider Physics, Cambridge Monographs on Particle Physics, Nuclear Physics, and Cosmology, Cambridge University Press, (2003), ISBN 9780521545891.
[6] D. J. Griffiths, Introduction to Elementary Particles, Physics Textbook, Wiley-VCH, (2008), ISBN 9783527406012.
[7] The LHC Higgs Cross Section Working Group Collaboration, S. Dittmaieret al., Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables,1101.0593.
[8] G. Aadet al.,An update to the combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC using up to 4.9 fb−1 of pp collision data at √
s = 7 TeV, Tech. Rep. ATLAS-CONF-2012-019, CERN, Geneva, (Mar 2012).
[9] The ATLAS Collaboration, G. Aad et al.,Combined search for the Standard Model Higgs boson using up to 4.9 fb-1 of pp collision data at sqrt(s) = 7 TeV with the ATLAS detector at the LHC, Phys.Lett.B710(2012) 49, 1202.1408.
[10] The Tevatron New Physics Higgs Working Group, CDF Collaboration, D0 Collaboration Collaboration, C. Group, D. Collaborations, the Tevatron New Physics, and H. Working, Updated Combination of CDF and D0 Searches for Standard Model Higgs Boson
Production with up to 10.0 fb−1 of Data,1207.0449.
[11] R. Gavin, Y. Li, F. Petriello, and S. Quackenbush, FEWZ 2.0: A code for hadronic Z production at next-to-next-to-leading order, Comput.Phys.Commun.182 (2011) 2388, 1011.3540.
[12] The ATLAS Collaboration, G. Aad et al.,Measurement of the W →lν and Z/γ∗ →ll production cross sections in proton-proton collisions at √
s= 7 TeV with the ATLAS detector,1010.2130, CERN-PH-EP-2010-037.
[13] L. Evans and P. Bryant, LHC Machine, Journal of Instrumentation3(08)(2008) S08001.
[14] A. Dusto,Making Heavy Ion Beams for the LHC, Available online, Published on 11 Nov 2011.
[15] O. S. Bruening, P. Collier, P. Lebrun, S. Myers, R. Ostojic, J. Poole, and P. Proudlock, LHC Design Report Volume I, CERN, Geneva, (2004).
[16] M. Benedikt, P. Collier, V. Mertens, J. Poole, and K. Schindl,LHC Design Report Volume III, CERN, Geneva, (2004).
[17] G. Aadet al.,Characterization of Interaction-Point Beam Parameters Using the pp Event-Vertex Distribution Reconstructed in the ATLAS Detector at the LHC, Tech. Rep.
ATLAS-CONF-2010-027, CERN, Geneva, (May 2010).
[18] G. Aadet al.,Updated Luminosity Determination in pp Collisions at root(s)=7 TeV using the ATLAS Detector, Tech. Rep. ATLAS-CONF-2011-011, CERN, Geneva, (Mar 2011).
[19] G. Aadet al.,Luminosity Determination in pp Collisions at sqrt(s) = 7 TeV using the ATLAS Detector in 2011, Tech. Rep. ATLAS-CONF-2011-116, CERN, Geneva, (Aug 2011).
[20] The ATLAS Collaboration, G. Aad et al.,The ATLAS Experiment at the CERN Large Hadron Collider, Journal of Instrumentation3(08)(2008) S08003.
[21] G. Aadet al.,ATLAS detector and physics performance: Technical Design Report, 1, Technical Design Report ATLAS, CERN, Geneva, (1999), Electronic version not available.
[22] G. Aadet al.,ATLAS muon spectrometer: Technical Design Report, Technical Design Report ATLAS, CERN, Geneva, (1997), distribution.
[23] G. Aadet al.,ATLAS level-1 trigger: Technical Design Report, Technical Design Report ATLAS, CERN, Geneva, (1998).
[24] The ATLAS Collaboration, G. Aad et al.,Performance of the ATLAS Trigger System in 2010, The European Physical Journal C - Particles and Fields 72(2012) 1,1110.1530, 10.1140/epjc/s10052-011-1849-1.
[25] Information Service page, http://atlas-onlsw.web.cern.ch/Atlas-onlsw/components/is/.
[26] A. Dotti, P. Adragna, D. C. Cimino, M. Della Pietra, R. Ferrari, G. Gaudio, C. Roda, D. Salvatore, W. R. Vandelli, and P. F. Zema,OHP: An Online Histogram Presenter for the ATLAS experiment, Tech. Rep. ATL-DAQ-CONF-2006-006.
ATL-COM-DAQ-2006-014, CERN, Geneva, (Mar 2006).
[27] Online Histogramming page, http://atlas-onlsw.web.cern.ch/Atlas-onlsw/oh/oh.htm.
[28] A. Corso-Radu, H. Havadand, Y. Ilchenko, S. Kolos, H. Okawa, K. Slagle, and A. Taffard, Data Quality Monitoring Framework for ATLAS Experiment: Performance Achieved with Colliding Beams at LHC, Tech. Rep. ATL-DAQ-PROC-2011-007, CERN, Geneva, (Jan 2011).
[29] Grid Computing page, Available online.
150
[30] G. Aadet al.,Atlas Computing: technical design report, CERN, Geneva, (2005).
[31] T. Maeno,PanDA: distributed production and distributed analysis system for ATLAS, Journal of Physics: Conference Series119(6) (2008) 062036.
[32] The PanDA Production and Distributed Analysis System,
https://twiki.cern.ch/twiki/bin/viewauth/Atlas/PanDA, ATLAS internal twiki.
[33] A. Krasznahorkay, D. Berge, J. Haller, S. Ask, N. Berger, T. Eifert, and A. Hoecker, SFrame ROOT/PROOF analysis framework,
http://sourceforge.net/apps/mediawiki/sframe/.
[34] The The GEANT4 Collaboration, S. Agostinelliet al.,GEANT4: A simulation toolkit, Nucl. Instrum. Meth. A506(2003) 250.
[35] Experimental Particle Physicists at Imperial College London,
http://imperialhep.blogspot.de/2011/08/strangeness-at-lhcb.html, Imperial’s LHCb blog.
[36] CTEQ, http://www.phys.psu.edu/ cteq/, CTEQ site.
[37] MRST, http://mstwpdf.hepforge.org/, MRST site.
[38] Neural Network Parton Distribution Functions, http://nnpdf.hepforge.org/, NNPDF site.
[39] A. D. Martin, W. J. Stirling, R. S. Thorne, and G. Watt,Parton distributions for the LHC, Eur.Phys.J.C63 (2009) 189,0901.0002.
[40] M. Dobbs, S. Frixione, E. Laenen, K. Tollefson, H. Baer, et al.,Les Houches guidebook to Monte Carlo generators for hadron collider physics,hep-ph/0403045, Compiled by the Working Group on Quantum Chromodynamics and the Standard Model.
[41] M. E. Peskin and D. V. Schroeder, An Introduction To Quantum Field Theory, Advanced Book Program, Addison-Wesley Publishing Company, (1995), ISBN 9780201503975.
[42] M. L. Mangano, F. Piccinini, A. D. Polosa, M. Moretti, and R. Pittau,ALPGEN, a generator for hard multiparton processes in hadronic collisions, Journal of High Energy Physics2003(07) (2003) 001.
[43] M. L. Mangano, M. Moretti, F. Piccinini, R. Pittau, and A. Polosa, AlpGEN, http://mlm.home.cern.ch/mlm/alpgen/, AlpGEN homepage.
[44] G. Corcellaet al.,HERWIG 6.5, JHEP0101(2001) 010.
[45] J. Butterworth, J. Forshaw, M. Seymour, and R. Walker,JIMMY, http://jimmy.hepforge.org/, JIMMY site.
[46] T. Sjostrand, S. Mrenna, and P. Skands, PYTHIA,
http://home.thep.lu.se/ torbjorn/Pythia.html, PYTHIA site.
[47] S. Moretti, K. Odagiri, P. Richardson, M. Seymour, and B. Webber, HERWIG, http://hepwww.rl.ac.uk/theory/seymour/herwig/, HERWIG site.
[48] G. Aadet al.,First tuning of HERWIG/JIMMY to ATLAS data, ATL-PHYS-PUB-2010-014.
[49] S. Gieseke, A. Ribon, P. Richardson, M. Seymour, B. Webber, and P. Stephens, HERWIG++, http://herwig.hepforge.org/, HERWIG++ site.
[50] S. Jadach, Z. Was, R. Decker, and J. H. K¨uhn,Theτ decay library TAUOLA, version 2.4.
[51] R. Decker, S. Jadach, M. Jezabek, J. Kuhn, and Z. Was, TAUOLA, http://wasm.home.cern.ch/wasm/goodies.html, TAUOLA site.
[52] P. Golonka and Z. Was, PHOTOS Monte Carlo: A Precision tool for QED corrections in Z and W decays., Eur. Phys. J. C45 (2006) 97.
[53] The ATLAS Collaboration, G. Aad et al.,Electron performance measurements with the ATLAS detector using the 2010 LHC proton-proton collision data,1110.3174.
[54] G. Aadet al.,Expected electron performance in the ATLAS experiment, Tech. Rep.
ATL-PHYS-PUB-2011-006, CERN, Geneva, (Apr. 2011).
[55] G. Aadet al.,Observation of Z →τhτl Decays with the ATLAS detector, Tech. Rep.
ATLAS-CONF-2011-010, CERN, Geneva, (Feb 2011).
[56] G. Aadet al.,Z→τ τ cross section measurement in proton-proton collisions at 7 TeV with the ATLAS experiment, Tech. Rep. ATLAS-CONF-2012-006, CERN, Geneva, (Feb 2012).
[57] M. Verducci, M. Cirilli, O. Kortner, D. Orestano, F. Petrucci, J. Rothberg, N. van Eldik, Z. van Kesteren, and M. Woudstra,Conditions Database and Calibration Software Framework for ATLAS Monitored Drift Tube Chambers, in: Nuclear Science Symposium Conference Record, 2006. IEEE, vol. 1, (Nov. 2006), 2006 622 –626.
[58] T. Lagouri, D. Adams, K. Assamagan, M. Biglietti, G. Carlino, G. Cataldi, F. Conventi, A. Farilla, Y. Fisyak, S. Goldfarb, E. Gorini, K. Mair, L. Merola, A. Nairz, A. Poppleton, M. Primavera, S. Rosati, J. Shank, S. Spagnolo, L. Spogli, G. Stavropoulos, M. Verducci, and T. Wenaus,A muon identification and combined reconstruction procedure for the ATLAS detector at the LHC at CERN, Nuclear Science, IEEE Transactions on 51(6) (Dec 2004) 3030 .
[59] G. Aadet al.,Expected performance of the ATLAS experiment: detector, trigger and physics, CERN, Geneva, (2009).
[60] G. Aadet al.,Determination of the muon reconstruction efficiency in ATLAS at the Z resonance in proton-proton collisons at sqrt(s)=7 TeV, Tech. Rep.
ATLAS-CONF-2011-008, CERN, Geneva, (Feb 2011).
[61] O. Kortner, O. Liebig, and E. Moyse,Muon Reconstruction Efficiency and Momentum Resolution of the ATLAS Experiment in Proton-Proton Collisions at√
s= 7 TeV in 2010, Tech. Rep. ATL-COM-PHYS-2012-069, CERN, Geneva, (Jan 2012), ATLAS internal.
[62] R. Nicolaidou, L. Chevalier, S. Hassani, J. F. Laporte, E. L. Menedeu, and A. Ouraou, Muon identification procedure for the ATLAS detector at the LHC using Muonboy reconstruction package and tests of its performance using cosmic rays and single beam data, Journal of Physics: Conference Series 219(3)(2010) 032052.
152
[63] D. Adams, K. A. Assamagan, M. Biglietti, G. Carlino, G. Cataldi, F. Conventi, A. Farilla, Y. Fisyak, S. Goldfarb, E. Gorini, T. Lagouri, K. Mair, L. Merola, A. Nairz, A. Poppleton, M. Primavera, S. Rosati, J. T. Shank, S. Spagnolo, L. Spogli, G. D. Stavropoulos,
M. Verducci, and T. Wenaus,Track reconstruction in the ATLAS Muon Spectrometer with MOORE 007, Tech. Rep. ATL-SOFT-2003-007, CERN, Geneva, (May 2003).
[64] S. Tarem, Z. Tarem, N. Panikashvili, and O. Belkind,MuGirl – Muon identification in the ATLAS detector from the inside out, in: Nuclear Science Symposium Conference Record, 2006. IEEE, vol. 1, (Nov 2006), 2006 617 –621.
[65] O. Kortner, E. Moyse, and A. Salvucci, Muon resolution plots, Tech. Rep.
ATL-COM-PHYS-2011-1504, CERN, Geneva, (Nov 2011).
[66] The ATLAS Collaboration, G. Aad et al.,Jet energy measurement with the ATLAS detector in proton-proton collisions at sqrt(s) = 7 TeV,1112.6426.
[67] G. Aadet al.,Properties of Jets and Inputs to Jet Reconstruction and Calibration with the ATLAS Detector Using Proton-Proton Collisions at √
s= 7 TeV, Tech. Rep.
ATLAS-CONF-2010-053, CERN, Geneva, (Jul 2010).
[68] M. Cacciari, G. P. Salam, and G. Soyez,The Anti-k(t) jet clustering algorithm, JHEP 0804(2008) 063,0802.1189.
[69] G. Aadet al.,Data-Quality Requirements and Event Cleaning for Jets and Missing Transverse Energy Reconstruction with the ATLAS Detector in Proton-Proton Collisions at a Center-of-Mass Energy of sqrts= 7 TeV, Tech. Rep. ATLAS-CONF-2010-038, CERN, Geneva, (Jul 2010).
[70] G. Aadet al.,Validating the measurement of jet energies with the ATLAS detector using Z + jet events from proton-proton collisions at sqrt(s) = 7 TeV, Tech. Rep.
ATLAS-CONF-2011-159, CERN, Geneva, (Dec 2011).
[71] G. Aadet al.,Jet energy resolution and selection efficiency relative to track jets from in-situ techniques with the ATLAS Detector Using Proton-Proton Collisions at a Center of Mass Energysqrts = 7 TeV, Tech. Rep. ATLAS-CONF-2010-054, CERN, Geneva, (Jul 2010).
[72] The ATLAS Collaboration, G. Aad et al.,Performance of Missing Transverse Momentum Reconstruction in Proton-Proton Collisions at 7 TeV with ATLAS, Eur.Phys.J.C72 (2012) 1844,1108.5602.
[73] G. Aadet al.,Reconstruction and Calibration of Missing Transverse Energy and Performance in Z and W events in ATLAS Proton-Proton Collisions at 7 TeV, Tech.
Rep. ATLAS-CONF-2011-080, CERN, Geneva, (Jun 2011).
[74] M. Cacciari and G. P. Salam,Dispelling the N3 myth for the kt jet-finder, Phys.Lett.
B641(2006) 57,hep-ph/0512210.
[75] W. Lampl, S. Laplace, D. Lelas, P. Loch, H. Ma, S. Menke, S. Rajagopalan, D. Rousseau, S. Snyder, and G. Unal,Calorimeter Clustering Algorithms: Description and
Performance, Tech. Rep. ATL-LARG-PUB-2008-002, ATL-COM-LARG-2008-003, CERN, Geneva, (Apr 2008).
[76] T. Barillari, E. Bergeaas Kuutmann, T. Carli, J. Erdmann, P. Giovannini, K. J. Grahn, C. Issever, A. Jantsch, A. Kiryunin, K. Lohwasser, A. Maslennikov, S. Menke,
H. Oberlack, G. Pospelov, E. Rauter, P. Schacht, F. Spano, P. Speckmayer, P. Stavina, and P. Strizenec,Local Hadronic Calibration, Tech. Rep. ATL-LARG-PUB-2009-001-2, ATL-COM-LARG-2008-006, CERN, Geneva, (Jun 2008).
[77] G. Aadet al.,Performance of the Reconstruction and Identification of Hadronic Tau Decays with ATLAS, Tech. Rep. ATLAS-CONF-2011-152, CERN, Geneva, (Nov 2011).
[78] G. Aadet al.,Reconstruction, Energy Calibration, and Identification of Hadronically
[78] G. Aadet al.,Reconstruction, Energy Calibration, and Identification of Hadronically