Dijet rapidity regions

Different rapidity regions of dijet event. This figure was inspired by D. Savoiu. For more related figures, please see the “jet” tag Particle Physics category. The cones are constructed with the tangent methods presented here.

The basic for-loop is

  \foreach \i [evaluate={\y=\i-0.5}] in {1,...,\N}{
    \foreach \j [evaluate={\x=\j-0.5;
                           \ang=60*(\i-1)/(\N-1); % seperation
                           \dang=90-60*(\j-1)/(\N-1); % boost
                 }] in {1,...,\N}{
      \draw[->,thick] (\x,\y) --++ (\ang-\dang:0.48); % bottom jet
      \draw[->,thick] (\x,\y) --++ (\ang+\dang:0.48); % top jet
      \fill[red] (\x,\y) circle(0.04);

Edit and compile if you like:

% Author: Izaak Neutelings (October 2021)
% Description: Rapidity regions of dijet events
% Inspiration:
%  Daniel Savoiu, https://indico.cern.ch/event/1073619/#5-update-on-dijet-production-s
\usepackage{listofitems} % for \readlist to create arrays
\usepackage[outline]{contour} % glow around text
\usetikzlibrary{math} % for \tikzmath
\tikzset{>=latex} % for LaTeX arrow head


  \edef\vang{\pgfmathresult} % angle of vector OV
    coordinate \C;
    \C = (#2)-(#3);
    \x = veclen(\Cx,\Cy)*\e*sin(\ang)^2; % x coordinate P
    \y = tan(\ang)*(veclen(\Cx,\Cy)-\x); % y coordinate P
    \a = veclen(\Cx,\Cy)*sqrt(\e)*sin(\ang); % vertical radius
    \b = veclen(\Cx,\Cy)*tan(\ang)*sqrt(1-\e*sin(\ang)^2); % horizontal radius
    \angb = acos(sqrt(\e)*sin(\ang)); % angle of P in ellipse
  \coordinate (tmpL) at ($(#3)-(\vang:\x pt)+(\vang+90:\y pt)$); % tangency
  \coordinate (tmpO) at ($(#2)+(\vang:0.01)$); % origin shifted
  \coordinate (tmpO') at ($(#2)+(\vang:0.02)$); % origin shifted 2
  \draw[thin,#1!40!black,rotate=\vang, %,fill=#1!50!black!80
    top color=#1!60!black!90,bottom color=#1!70!black!75,shading angle=\vang]
    (#3) ellipse({\a pt} and {\b pt});
  top color=#1!90!black!40,bottom color=#1!40!black!60,shading angle=\vang]
    (tmpL) arc(180-\angb:180+\angb:{\a pt} and {\b pt})
    -- (tmpO) -- cycle;
\def\tick#1#2{\draw[thick] (#1) ++ (#2:0.1) --++ (#2-180:0.2)}



  \readlist\cols{blue,green,myorange,red,mypurple} % list of colors
  \foreach \i [evaluate={\y=\i-0.5; \ym=0.5*(\i-1); \Nx=\N-\i+1; \e=0.5*\i}] in {1,...,\N}{
    \draw[very thin,dashed,black!50] (0,\i) --++ (\Nx,0);
    \draw[very thin,dashed,black!50] (\i,0) --++ (0,\Nx);
      (\i-1,0) --++ (135:{sqrt(2)*(\i+0.2)}) coordinate (T\i) --++ (45:{sqrt(2)/2});
    \draw[mygray] (T\i) --++ (135:0.06) node[above=-2,rotate=45] {\ym};
    \tick{0,\i}{0} node[left=-1,scale=0.9] {\e};
    \tick{\i,0}{90} node[below=-1,scale=0.9] {\e};
  \draw[mygray] (\N,0) --++ (135:{sqrt(2)*(\N+0.75)}) node[right=3,above=0,rotate=45] {2.5};
  % JETS
  \foreach \i [evaluate={\y=\i-0.5; \Nx=\N-\i+1; \e=0.5*\i}] in {1,...,\N}{
    \foreach \j [evaluate={\x=\j-0.5; \mix=100-60*(\j-1)/(\N-1);
                           \ang=60*(\i-1)/(\N-1); % seperation
                           \dang=90-60*(\j-1)/(\N-1); % boost
                 }] in {1,...,\Nx}{
      \colorlet{conecol}{\cols[\i]!\mix} % color for cone
      \coordinate (O) at (\x,\y); % primary vertex
      \coordinate (T) at ($(\x,\y)+(\ang+\dang:0.42)$); % top jet
      \coordinate (B) at ($(\x,\y)+(\ang-\dang:0.42)$); % bottom jet
      \jetcone[conecol]{O}{T}{30}{0.06} %!70!white
  % AXIS
    (0,1.1*\N) %node[left] {\contour{white}{$y*$}} --
    node[left=6,above right=-3] {$y^* = \frac{1}{2}|y_1-y_2|$} --
    (0,0) -- (1.1*\N,0) node[right] {$y_\text{b} = \frac{1}{2}|y_1+y_2|$};
    (135:4.0) --++ (45:1.3)
    node[pos=0.7,above,rotate=45] {$|y_\text{max}|$};


Click to download: jet_eta.texjet_eta.pdf
Open in Overleaf: jet_eta.tex

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