$\gamma p\to \pi \Delta$

We present the model published in [Nys18a] modelling the reactions \begin{equation} \gamma p\to \pi^- \Delta^{++} \qquad \text{and} \qquad \gamma p\to \pi^+ \Delta^{0} \end{equation} We report here only the main features of the model.
The code can be downloaded in Resources section and simulated in the Simulation section.

References

[Nys18a] J. Nys, et al (JPAC), ``Features of $\pi \Delta$ Photoproduction at High Energies,'' Phys. Lett. B 779, 77 (2018)

Resources

  1. par_simu.txt:
    The simulation parameters are $E_\gamma$, $\beta_V$, $\beta_A$, iso, $isGJ$.
    iso = 0,1 for $f_2$ / $a_2$ photoproduction.
  2. sdme0.txt and sdme1.txt:
    $-t$ (GeV$^2$), $\rho^{0,1}_{00}$, $\rho^{0,1}_{11}$, $\rho^{0,1}_{22}$, $\rho^{0,1}_{10}$, Re $\rho^{0,1}_{1-1}$, Re $\rho^{0,1}_{20}$, Re $\rho^{0,1}_{21}$, Re $\rho^{0,1}_{2-1}$, Re$\rho^{0,1}_{2-2}$
  3. sdme2.txt:
    $-t$ (GeV$^2$), Im $\rho^2_{10}$, Im $\rho^2_{1-1}$, Im $\rho^2_{20}$, Im $\rho^2_{21}$, Im $\rho^2_{2-1}$, Im $\rho^2_{2-2}$
  4. sdme_nat.txt and sdme_unn.txt:
    $-t$, $\rho^{(\pm)}_{00}$, $\rho^{(\pm)}_{11}$, $\rho^{(\pm)}_{22}$, $\rho^{(\pm)}_{10}$, Re $\rho^{(\pm)}_{1-1}$, Re $\rho^{(\pm)}_{20}$, Re $\rho^{(\pm)}_{21}$, Re $\rho^{(\pm)}_{2-1}$, Re$\rho^{(\pm)}_{2-2}$
  5. obs.txt:
    $-t$ (GeV$^2$), $d\sigma/dt$ ($\mu$b/GeV$^2$), $\Sigma_{4\pi}$, $P_\sigma$

Simulation

The user can choose the beam energy (in the target rest frame), the final state and the frame in which the SDME are computed.
The differential cross and the beam asymmetry and frame independent.

Simulation specification:
Final state:
Model:
Frame:

'; // print horizontal line echo '

Results

'; // simulation parameters $Eg = $_POST["Eg"]; $iso = $_POST["iso"]; $mod = $_POST["MD"]; $frame = $_POST["FR"]; echo "Simulation at Eg = ", $Eg, " GeV
"; switch ($iso){ case -1: echo "Photoproduction of pi- Delta++
"; break; case +1: echo "Photoproduction of pi+ Delta0
"; break; } switch ($mod){ case 0: echo "The pole model
"; break; case 1: echo "The cut model
"; break; } switch ($frame){ case 1: echo "SDME in the helicity frame

"; break; case 0: echo "SDME in the GJ frame

"; break; } $rootPath = getcwd(); // change the directory chdir('PiDelta'); // because the execution write files // in the current directory // print the simulation parameters in simu.txt $data = array($mod, " ",$iso, " ", $Eg, " ", $frame); // t range is fixed file_put_contents("simu.txt", $data); exec('./PiDelta.exe'); // run the program switch ($frame){ case 1: $ret = system('gnuplot44 gnuplotH.txt ', $response); $ret = system('gnuplot44 gnuplotH_Nat.txt ', $response); break; case 0: $ret = system('gnuplot44 gnuplotGJ.txt ', $response); $ret = system('gnuplot44 gnuplotGJ_Nat.txt ', $response); break; } echo "The x-axis of the plots is $\sqrt{-t'}$ in GeV.
"; // Download the plot echo "Download the output file and the plots of the cross section and beam asymetry: obs.txt , resultsGJ.txt
"; switch ($frame){ case 1: echo "Download the output file and the plot for the SDME (helicity frame): sdme_H.txt , plotH.png , plotH_Nat.png
"; break; case 0: echo "Download the output file and the plots for the SDME (GJ frame): sdme_GJ.txt , plotGJ.png , plotGJ_Nat.png
"; break; } // Display the plots echo "

"; //echo " "; //echo " "; echo "

"; switch ($frame){ case 1: echo " "; echo " "; break; case 0: echo " "; echo " "; break; } chdir($rootPath); // go back to root directory } if(isset($_POST['submit'])) // call the function display if something is submitted { display(); } ?>

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Designed by Vincent Mathieu

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