Annotation of ttbar/p20_taujets_note/Strategy_and_Dataset.tex, revision 1.1
1.1 ! uid12904 1:
! 2: \section{Strategy}
! 3:
! 4:
! 5: \subsection{\label{sub:Signal-characteristics}Signal characteristics}
! 6:
! 7:
! 8: \subsubsection{Parton level MC}
! 9:
! 10: First of all we want to examine the properties of our signal. For
! 11: these purposes we used MC simulated samples (\textasciitilde{}10K
! 12: events each) generated with ALPGEN \cite{ALPGEN} interfaced to Pythia
! 13: \cite{PYTHIA} for showering and fragmentation.
! 14:
! 15:
! 16: \paragraph{$t\bar{t}$}
! 17:
! 18: First of all we wanted to look at the properties of the top quark
! 19: itself. Figure \ref{t-jets} shows the $\eta$, $\phi$ and $P_{T}$
! 20: distributions.
! 21:
! 22: %
! 23: \begin{figure}
! 24: \subfigure[$P_{T}$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_tjets}}\subfigure[$\eta$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_tjets}}
! 25:
! 26: \subfigure[$\phi$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/phi_tjets}}
! 27:
! 28:
! 29: \caption{Properties of t-quarks at the parton level in signal MC sample, $P_{T}$>
! 30: 15 GeV}
! 31:
! 32: \begin{centering}\label{t-jets}\par\end{centering}
! 33: \end{figure}
! 34:
! 35:
! 36:
! 37: \paragraph{$\tau$ and $\not\!\! E_{T}$}
! 38:
! 39: The unique property of $\tau$ (compared to other leptons) is that
! 40: it emits neutrino in its decay before it even reaches detector volume,
! 41: contributing to the missing energy of the event. For this reason the
! 42: $\tau$, available for measurement is not the same as physical $\tau$
! 43: produced. Figure \ref{cap:MC taus} demonstrates how a sizable fraction
! 44: of $\tau$ momentum goes missing. The plots of $\tau$ $\eta$ (Figure
! 45: \ref{cap:MC taus}) and transverse mass with $\not\!\! E_{T}$ thus
! 46: are done for the visible part of $\tau$
! 47:
! 48: This is to be compared with the $e+jets$ channel (Figure \ref{cap:MC elecs}).
! 49: As one can observe, the {}``total'' $\tau$ leptons behave very
! 50: simmilar to electrons, as of cause expected. However, after taking
! 51: into account the lost part of the $\tau$ energy situation becomes
! 52: very different.
! 53:
! 54: %
! 55: \begin{figure}
! 56: \subfigure[Parton level $\not E_{T}$ for the signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/met_mc}}
! 57: \subfigure[mT of MC $\tau$ and $\not E_{T} $ (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/mt_tau_met_mc}}
! 58:
! 59: \subfigure[$\eta$ of the MC $\tau$ in signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_tau_mc}}
! 60: \subfigure[$P_{T}$ of the MC $\tau$ in signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_tau_mc}}
! 61:
! 62: \subfigure[Visible energy fraction of $\tau$ in signal MC]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/visable_fraction}}
! 63:
! 64:
! 65: \caption{Properties of $\not\!\! E_{T}$ and $\tau$ at the parton level in
! 66: signal MC sample}
! 67:
! 68: \begin{centering}\label{cap:MC taus}\par\end{centering}
! 69: \end{figure}
! 70:
! 71:
! 72: %
! 73: \begin{figure}
! 74: \subfigure[Parton level $\not E_{T}$ for the signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/met_mc_elec}}
! 75: \subfigure[mT of MC electron and $\not E_{T} $ (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/mt_tau_met_mc_elec}}
! 76:
! 77: \subfigure[$\eta$ of the MC electron in signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_tau_mc_elec}}
! 78: \subfigure[$P_{T}$ of the MC electron in signal MC (red is total, green- visible)]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_tau_mc_elec}}
! 79:
! 80:
! 81: \caption{Properties of $\not\!\! E_{T}$ and electron at the parton level
! 82: in $t\bar{t}\rightarrow e+jets$ MC sample}
! 83:
! 84: \begin{centering}\label{cap:MC elecs}\par\end{centering}
! 85: \end{figure}
! 86:
! 87:
! 88:
! 89: \paragraph{Jets}
! 90:
! 91: b - jets are shown on Figure \ref{b-jets} while the product of W
! 92: decay are shown on Figure \ref{not b-jets}. This however doesn't
! 93: account for all the jets that will be reconstructed. Figure \ref{not b-jets-all}
! 94: demonstrates all the non-b quarks and gluons in a $t\bar{t}$ event.
! 95:
! 96: %
! 97: \begin{figure}
! 98: \subfigure[Number of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/nbquarks}}
! 99: \subfigure[$P_{T}$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_bjets}}
! 100:
! 101: \subfigure[$\eta$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_bjets}}
! 102: \subfigure[$\phi$ of b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/phi_bjets}}
! 103:
! 104:
! 105: \caption{Properties of b-quarks at the parton level in signal MC sample, $P_{T}$>
! 106: 15 GeV}
! 107:
! 108: \begin{centering}\label{b-jets}\par\end{centering}
! 109: \end{figure}
! 110:
! 111:
! 112: %
! 113: \begin{figure}
! 114: \subfigure[Number of light quarks from the W decay]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/nlightquarks}}
! 115: \subfigure[$P_{T}$ of light quarks from the W decay]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_notbjets}}
! 116:
! 117: \subfigure[$\eta$ of light quarks from the W decay]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_notbjets}}
! 118: \subfigure[$\phi$ of light quarks from the W decay]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/phi_notbjets}}
! 119:
! 120:
! 121: \caption{Properties of light quarks from the W decay at the parton level in
! 122: signal MC sample, $P_{T}$> 15 GeV}
! 123:
! 124: \begin{centering}\label{not b-jets}\par\end{centering}
! 125: \end{figure}
! 126:
! 127:
! 128: %
! 129: \begin{figure}
! 130: \subfigure[Number of not b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/nlightquarks_all}}
! 131: \subfigure[$P_{T}$ of not b-quarks]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_notbjets_all}}
! 132:
! 133: \subfigure[$\eta$ of not b-quarks ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_notbjets_all}}
! 134: \subfigure[$\phi$ of not b-quarks ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/phi_notbjets_all}}
! 135:
! 136:
! 137: \caption{Properties of all the light quarks and gluons in an event at the
! 138: parton level in signal MC sample, $P_{T}$> 15 GeV}
! 139:
! 140: \begin{centering}\label{not b-jets-all}\par\end{centering}
! 141: \end{figure}
! 142:
! 143:
! 144:
! 145: \subsubsection{Detector signature (reconstructed Monte Carlo)}
! 146:
! 147: Now we need to find out how well our experiment observes and reconstructs
! 148: this physical process. The $t\bar{t}\rightarrow\tau+jets$ Monte Carlo
! 149: file was processed through the detailed D0 Detector simulation. Jets
! 150: are reconstructed, using 0.5 radius cone (in $\eta-\phi$). Taus are
! 151: identified using tau ID algorithm and we apply 0.8 cut on the $\tau$
! 152: selection neural net (section \ref{sub:tau--ID}).
! 153:
! 154:
! 155: \paragraph{$\tau$ and $\not\!\! E_{T}$}
! 156:
! 157: We can see that for reconstructed $\tau$'s $mT(of$ $\tau$ $and$
! 158: $\not E_{T})$ (Figure \ref{cap:reco tau}) doesn't look as good as
! 159: for MC taus (Figure \ref{cap:MC taus}). We observe a noticeable \char`\"{}tail\char`\"{}
! 160: above 80 GeV.
! 161:
! 162: %
! 163: \begin{figure}
! 164: \subfigure[Reconstructed $\not E_{T}$ for the signal MC ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/met_reco}}
! 165: \subfigure[mT of MC $\tau$ and $\not E_{T} $ reconstructed ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/mt_tau_met_reco}}
! 166:
! 167: \subfigure[$\eta$ of the MC tau in signal MC reconstructed ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_tau_reco}}
! 168: \subfigure[ $P_{T}$ of the $\tau$ ]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/pt_tau_reco}}
! 169:
! 170:
! 171: \caption{Properties of detector reconstructed $\not\!\! E_{T}$ and $\tau$
! 172: in signal MC sample}
! 173:
! 174: \begin{centering}\label{cap:reco tau}\par\end{centering}
! 175: \end{figure}
! 176:
! 177:
! 178:
! 179: \paragraph{Jets}
! 180:
! 181: Before b-tagging (section \ref{sub:B-tagging}) one can't separate
! 182: b-jets from non-b jets, so we don't make a distinction at this point.
! 183: Most important variables are the number of jets and $\eta$ and $P_{T}$
! 184: distributions (Figure \ref{jets1}).
! 185:
! 186: %
! 187: \begin{figure}
! 188: \subfigure[Number of jets]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/njets}}
! 189: \subfigure[$P_{T}$ of jets]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jetpt}}
! 190:
! 191: \subfigure[$\eta$ of jets]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/eta_jets}}
! 192: \subfigure[$\phi$ of jets]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/phi_jets}}
! 193:
! 194:
! 195: \caption{Properties of the jets in signal MC sample, $P_{T}$> 15 GeV}
! 196:
! 197: \begin{centering}\label{jets1}\par\end{centering}
! 198: \end{figure}
! 199:
! 200:
! 201: Jets are arranged in the order of their $P_{T}$: leading (highest),
! 202: sub-leading etc. We can see on Figure \ref{jets1} that we typically
! 203: have 4 or 5 jets in an event. It is interesting to compare the leading
! 204: jet to the fourth and fifth jets (Figure \ref{jets2}). We can see
! 205: that jets after the third are very soft, as expected.
! 206:
! 207: %
! 208: \begin{figure}
! 209: \subfigure[1st jet]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jet0pt}}
! 210: \subfigure[2nd jet]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jet1pt}}
! 211:
! 212: \subfigure[3rd jet]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jet2pt}}
! 213: \subfigure[4th jet]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jet3pt}}
! 214:
! 215: \subfigure[5th jet]{\includegraphics[scale=0.3]{MS_thesis/proposal_plots/jet4pt}}
! 216:
! 217:
! 218: \caption{$P_{T}$ distributions for jets in signal MC sample (including $\tau$)}
! 219:
! 220: \begin{centering}\label{jets2}\par\end{centering}
! 221: \end{figure}
! 222:
! 223:
! 224:
! 225: \subsection{Backgrounds}
! 226:
! 227: Two main distinctive features of the signal limit the spectrum of
! 228: important backgrounds. In order to be relevant the process must have
! 229: high (>3) number of jets as well as sizable (>15 GeV) $\not\!\! E_{T}$.
! 230: All the candidate processes are listed in Table \ref{backgrounds}.
! 231: The cross section listed include the branching fractions into $\tau$
! 232:
! 233: We can conclude that two dominant background sources are QCD ({}``fake
! 234: $\tau$'') and W+4jets. These two sources were taken into account
! 235: in these analysis.
! 236:
! 237: %
! 238: \begin{table}
! 239: \begin{tabular}{|l|l|c|}
! 240: \hline
! 241: \multicolumn{1}{||l|}{Background}&
! 242: \multicolumn{1}{||l|}{Description}&
! 243: \multicolumn{1}{||l||}{Cross Section}\tabularnewline
! 244: \hline
! 245: $W+jjjj\rightarrow\tau\nu jjjj$&
! 246: Has identical signature to the signal&
! 247: $\sim$18 pb \tabularnewline
! 248: \hline
! 249: $Z/\gamma+jjj\rightarrow\tau\tau jjj$ &
! 250: $\tau$ is usually found as a jet&
! 251: $\sim$2.6 pb\tabularnewline
! 252: \hline
! 253: $WZ\rightarrow\tau\nu jj$&
! 254: needs two extra jet (can be gluon emission) &
! 255: $\sim$0.2 pb\tabularnewline
! 256: \hline
! 257: $WW\rightarrow\tau\nu jj$&
! 258: needs two extra jet (can be gluon emission) &
! 259: $\sim$0.5 pb\tabularnewline
! 260: \hline
! 261: single top &
! 262: small cross section, but has b-jets &
! 263: $\sim$0.5 pb\tabularnewline
! 264: \hline
! 265: QCD &
! 266: Any 4-jet event, that doesn't have a real $\tau$ in it&
! 267: $>$100 nb \tabularnewline
! 268: \hline
! 269: \end{tabular}\centering
! 270:
! 271:
! 272: \caption{Background sources, relevant for the $\tau+jets$ analysis. Branching
! 273: into hadronic $\tau$ had been applied \cite{l+jets}}
! 274:
! 275: \label{backgrounds}
! 276: \end{table}
! 277:
! 278:
! 279:
! 280: \section{Dataset}
! 281:
! 282: As will be demonstrated in section \ref{sub:Running-trigsim} the
! 283: optimal (that is most efficient) combination of triggers for this
! 284: analysis is:
! 285:
! 286: \begin{itemize}
! 287: \item The Higgs Missing $H_{T}$ trigger (MHT30\_3CJT5)
! 288: \item The ALLJET trigger (4JT10)
! 289: \end{itemize}
! 290: Together they yield over 85\% signal acceptance and they'd been running
! 291: unprescaled for most of D0 stable operation.
! 292:
! 293: The data skim, utilizing both of these triggers would be optimal for
! 294: this analysis. Until the technical issues involved in its production
! 295: are fully resolved, we are using the ALLJET skim \cite{Luminosity},
! 296: which only contains the data, collected by the 4JT10 (and its subsequent
! 297: versions).
! 298:
! 299: Such skim is only 70\% efficient for the signal, but it's the closest
! 300: available for our needs at the moment. The full PASS2 ALLJET skim
! 301: had been processed through the standard D0 top group data quality
! 302: criteria, discarding bad luminosity blocks, at the same time computing
! 303: the recorded lumi. The results are represented in table \ref{lumi1}.
! 304: Therefore the total luminosity available for the analysis amounts
! 305: to $349\pm23$ $pb^{-1}$ \cite{alljet}
! 306:
! 307: %
! 308: \begin{table}
! 309: \begin{tabular}{|c|c|c|c|}
! 310: \hline
! 311: Stage&
! 312: Luminosity ($pb^{-1})$&
! 313: Relative Size (\%)&
! 314: Absolute Size (\%)\tabularnewline
! 315: \hline
! 316: \hline
! 317: Delivered&
! 318: 482.6&
! 319: 100&
! 320: 100\tabularnewline
! 321: \hline
! 322: Recorded&
! 323: 411.6&
! 324: 85.3&
! 325: 85.3\tabularnewline
! 326: \hline
! 327: Good&
! 328: 352.5&
! 329: 85.6&
! 330: 73.0\tabularnewline
! 331: \hline
! 332: Reconstructed&
! 333: 349.3&
! 334: 99.1&
! 335: 72.4\tabularnewline
! 336: \hline
! 337: \end{tabular}
! 338:
! 339:
! 340: \caption{The results of luminosity calculation for the PASS2 ALLJET top skim}
! 341:
! 342: \label{lumi1}
! 343: \end{table}
! 344:
! 345:
! 346: The table \ref{lumi2} demonstrates the breakdown of this luminosity
! 347: between the different trigger versions.
! 348:
! 349: %
! 350: \begin{table}
! 351: \begin{tabular}{|c|c|c|}
! 352: \hline
! 353: Trigger version&
! 354: Trigger name&
! 355: Luminosity ($pb^{-1})$\tabularnewline
! 356: \hline
! 357: \hline
! 358: 8.0&
! 359: 4JT10&
! 360: 19.4\tabularnewline
! 361: \hline
! 362: 9.0&
! 363: 4JT10&
! 364: 21.2\tabularnewline
! 365: \hline
! 366: 10.0&
! 367: 4JT10&
! 368: 15.1\tabularnewline
! 369: \hline
! 370: 11.0&
! 371: 4JT10&
! 372: 57.3\tabularnewline
! 373: \hline
! 374: 12.0&
! 375: 4JT12&
! 376: 196\tabularnewline
! 377: \hline
! 378: 13.0&
! 379: JT2\_4JT12L\_HT&
! 380: 13.5\tabularnewline
! 381: \hline
! 382: 13.1&
! 383: JT2\_4JT12L\_HT&
! 384: 27.8\tabularnewline
! 385: \hline
! 386: 13.3&
! 387: JT2\_4JT12L\_HT&
! 388: 0\tabularnewline
! 389: \hline
! 390: \end{tabular}
! 391:
! 392:
! 393: \caption{Luminosity of the ALLJET skim for different D0 trigger list versions}
! 394:
! 395: \label{lumi2}
! 396: \end{table}
! 397:
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