1 | \section{MC procedure.} |
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2 | |
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3 | \hspace{1.0em} |
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4 | At intermediate energies $\gamma$-nucleon and $\gamma$-nucleus interactions are |
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5 | performed within the hadron kinetic model similarly as the hadron-nucleon and |
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6 | hadron-nucleus interactions. |
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7 | |
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8 | At high energies the Monte Carlo procedure |
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9 | in the case of $\gamma$--nucleon collision can be |
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10 | outlined as follows: |
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11 | \begin{itemize} |
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12 | \item At given c.m. energy squared and at given virtuality $Q^2$ sample |
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13 | mass $M^2$ of |
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14 | hadronic $q\bar{q}$ fluctuation according to ($\ref{HEGI2}$) |
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15 | and sample its flavor |
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16 | according to statistical weights: $\omega_{u\bar{u}}= 1/2$, |
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17 | $\omega_{d\bar{d}}= 1/4$ and $\omega_{s\bar{s}}= 1/4$ are derived from |
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18 | ($\ref{HEGI3}$); |
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19 | \item Sample the momentum fraction $x$ of a valence quark inside |
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20 | a hadronic fluctuation |
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21 | according to |
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22 | \begin{equation} |
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23 | \label{GIMA1} \rho(x) \sim \frac{1}{\sqrt{x(1-x)}} |
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24 | \end{equation} |
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25 | and transverse momentum of a quark according to the Gaussian |
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26 | distribution as for hadrons; |
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27 | \item Split nucleon into quark and diquark as it was described |
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28 | for hadron-nucleon |
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29 | interaction; |
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30 | \item Create two strings spanned between quark from a hadronic fluctuation and |
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31 | diquark from nucleon and between antiquark from a hadronic |
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32 | fluctuation and quark from nucleon; |
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33 | \item Decay string into hadrons as it was described for |
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34 | hadron-nucleon interactions. |
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35 | \end{itemize} |
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36 | |
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37 | In the case of $\gamma$--nucleus collision the MC procedure is follows: |
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38 | \begin{itemize} |
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39 | \item At given c.m. energy squared and at given virtuality |
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40 | $Q^2$ sample mass $M^2$ of |
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41 | hadronic $q\bar{q}$ fluctuation and sample its flavor as it is done for |
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42 | $\gamma$--nucleon collision; |
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43 | |
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44 | \item Calculate coherence length $d$; |
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45 | |
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46 | \item If coherence length less than internucleon distance |
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47 | then simulate inelastic |
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48 | hadron fluctuation-nucleon collision at choosen impact |
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49 | parameter $B$ as was described |
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50 | above; |
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51 | |
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52 | \item If coherence length more than internucleon distance then |
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53 | perform simulation of hadron fluctuation-nucleus collision at choosen |
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54 | impact parameter $B$ using parton string model similarly as for meson-nucleus |
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55 | interactions. For this case the probability of inelastic collision of |
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56 | a hadron fluctuation with nucleon |
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57 | $i$ at given impact parameter ${\bf b}_i$ is calculated according to |
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58 | \begin{equation} |
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59 | \label{GIMA3} p_{VN}(s,b^2) = 1 - exp{[-2u(s, b^2)]}; |
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60 | \end{equation} |
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61 | with the eikonal $u(s,b^2)$ defined by Eq. ($\ref{HEGI7}$) at |
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62 | $Q^2 = 0$ and $M^2=M_{\rho}$. |
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63 | \end{itemize} |
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64 | |
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65 | |
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66 | |
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