\documentclass[hyperref=pdftex, presentation]{beamer} % Replacing 'presentation' with 'handout' in the above line % will produce 4 slides per page. % The hyperref option makes it possible to include hyperlinks. \mode { \usetheme{Boadilla} \setbeamercovered{transparent} } \usepackage[english]{babel} \usepackage[latin1]{inputenc} \usepackage{times} \usepackage[T1]{fontenc} \usepackage{wrapfig} \usepackage{graphicx} \mode{ \usepackage{pgfpages} \pgfpagesuselayout{4 on 1}[letterpaper,landscape,border shrink=5mm] \setbeamercolor{background canvas}{bg=black!10} } \setbeamertemplate{footline} { \leavevmode% \hbox{% \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{author in head/foot}% \usebeamerfont{author in head/ foot}\insertshortauthor%&\approx& (\insertshorti \end{beamercolorbox}% \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,center]{title in head/foot}% \usebeamerfont{title in head/foot}\insertshorttitle \end{beamercolorbox}% \begin{beamercolorbox}[wd=.333333\paperwidth,ht=2.25ex,dp=1ex,right]{date in head/foot}% \usebeamerfont{date in head/foot}\insertshortdate\hspace*{2em} \insertframenumber / \inserttotalframenumber\hspace*{2ex} \end{beamercolorbox}}% \vskip0pt% } \newcommand{\backupbegin}{ \newcounter{framenumberappendix} \setcounter{framenumberappendix}{\value{framenumber}} } \newcommand{\backupend}{ \addtocounter{framenumberappendix}{-\value{framenumber}} \addtocounter{framenumber}{\value{framenumberappendix}} } %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %\title[GEANT4/EGS5]{GEANT4/EGS5} \title{Global SVT alignment with Mollers} \author{Sho Uemura} \institute{SLAC} \date[May 20, 2016] \begin{document} \begin{frame} \titlepage \end{frame} \begin{frame}{SVT alignment} \begin{itemize} \item Local alignment (Millepede): move sensors around to minimize track $\chi^2$ \item Local alignment is blind to ``weak modes'' that uniformly shift track parameters without changing $\chi^2$ \begin{itemize} \item Each track parameter corresponds to a weak mode \end{itemize} \item Strategy: run local alignment, use tweaks to fix the global alignment, rerun local alignment for second-order corrections \item I'm assuming local alignment is perfect \item Global alignment: use external references to get things right \item SVT top and bottom each need to be aligned \end{itemize} \end{frame} \begin{frame}{Past work} \begin{itemize} \item Initial Millepede alignment gave very bad FEE momentum (O(10\%) shifts), inconsistent beamspots in top and bottom \item We developed formulas to ``tweak'' the alignment constants along each weak mode without disrupting local alignment \begin{itemize} \item Used SVT survey as a prior (if we can't constrain a weak mode, use the value that minimizes deviation from survey) \item Shove curvature to roughly the right place, make top and bottom beamspots agree at $z=0$ \end{itemize} \item What we didn't do: \begin{itemize} \item Think about how to assess global alignment (curvature is easy, everything else is hard) \item Get things exactly right \end{itemize} \item Current recon alignment has beamspot near $(0,0)$ and momentum within 2\%, nothing else was even checked \begin{itemize} \item Apparent beam tilt: real, or alignment? \item Vertex Z dependence on mass: clear sign of bad global alignment \end{itemize} \end{itemize} \end{frame} \begin{frame}{Doing global alignment right} \begin{itemize} \item External references: FEE momentum, beam axis, beam spot \begin{itemize} \item Set everything to nominal values for now, we can decide later if we need to tilt the beam or shift the beam spot \end{itemize} \item Get curvature right: correct the known FEE momentum shifts (Omar: 1.040 in top, 1.069 in bottom) \begin{itemize} \item Straight-throughs ought be a better way to constrain this \end{itemize} \item Use Moller two-body kinematics to do top and bottom separately \end{itemize} \end{frame} \begin{frame}{Mollers: $\theta$ vs. $E$} \begin{columns} \column{0.55\textwidth} \begin{itemize} \item Energy-angle relation: $\cos\theta=1-m_e(1/E-1/E_{beam})$ \item Cut on energy, get a ring centered around the beam axis \item We only have a bit of the ring: plot the $\theta$ residual against $\phi$, fit \begin{itemize} \item Constant term: vertical tilt (or energy, but we calibrated that already) \item Linear term: horizontal tilt \end{itemize} \item Repeat at different energies to make sure we're not getting biased by acceptance \end{itemize} % \begin{center} % \includegraphics[width=0.5\textwidth]{energy-angle} % \end{center} \column{0.45\textwidth} % \includegraphics[width=\textwidth]{e_theta} \includegraphics[width=\textwidth]{energy-angle} \includegraphics[width=\textwidth,page=1]{test_domega} \end{columns} \end{frame} \begin{frame}{Mollers: $\theta_y$ vs. $z_0$} \begin{itemize} \item Plot $y(z=0)$ against $\theta_y$, fit \begin{itemize} \item Constant term: vertical offset \item Linear term: Z offset \end{itemize} \item Looks like target is at negative Z and our earlier attempt at global alignment ``corrected'' by applying spurious shifts and tilts \end{itemize} \begin{center} \includegraphics[width=0.5\textwidth,page=4]{test_domega} \includegraphics[width=0.5\textwidth,page=3]{test_domega} \end{center} \end{frame} \begin{frame}{Mollers: $\theta_x$ vs. $d_0$} \begin{itemize} \item Plot $x(z=0)$ against $\theta_x$, fit? Too much momentum dependence \item Plot $x(z=0)$ against $p$ \item Fringe field? Why is the sign of the effect different in top and bottom? \end{itemize} \begin{center} \includegraphics[width=0.5\textwidth,page=8]{test_domega} \includegraphics[width=0.5\textwidth,page=7]{test_domega} \end{center} \end{frame} \begin{frame}{Work in progress} \begin{itemize} \item Need to compare with MC \item Need to improve sensitivity: would be nice to get $\sim$0.1 mrad for tilts and $\sim$1 mm for target Z, not quite there yet \item Cross-check against tridents and FEE \item Corrections can be applied to track parameters post-recon (I do this in my tuple maker); can be pushed into the alignment later \end{itemize} \end{frame} \end{document}