1 | \subsection{Quark or diquark annihilation in hadronic processes.} |
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2 | |
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3 | \hspace{1.0em} |
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4 | We consider also hadron-hadron inelastic processes when antiquark or |
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5 | antidiquark from hadron projectile annihilate with corresponding quark |
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6 | or diquark from hadron target. |
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7 | In this case excitation of one baryonic (string with quark and diquark |
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8 | ends) or mesonic (string with quark and antiquark ends) is created, |
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9 | respectively. These processes in the Regge theory correspond to cut |
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10 | reggeon exchange diagrams. Initial energy $\sqrt{s}$ |
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11 | dependences of these processes |
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12 | cross sections are defined by intercepts of reggeon exchange trajectories. |
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13 | For example $\sigma_{\pi^{+}p\rightarrow S(s)} \sim s^{\alpha_{\rho}(0)-1}$, |
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14 | $S$ notes string and $\alpha_{\rho}(0)$ is the intercept of $\rho$ reggeon |
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15 | trajectory. Thus $\sigma_{\pi^{+}p\rightarrow S(s)} |
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16 | $ decreases with energy |
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17 | rise. Cross sections for other quark and diquark proccesses have simiar |
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18 | as $\sigma_{\pi^{+}p\rightarrow S(s)}$ initial energy dependences. |
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19 | Thus quark and diquark annihilation processes are important at |
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20 | relative low initial energies. Another example of these processes is |
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21 | $\bar{p}p \rightarrow S$, which is used in the kinetic model to describe |
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22 | final state of $\bar{p}p$ annihilation. |
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23 | Simulation of such kind process is rather simple. We should randomly |
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24 | (according to weight calculated using hadron wave function) |
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25 | choose quark (antiquark) or diquark (antidiquark) from projectile and |
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26 | find suitable (with the same flavor content) partner for annihilation |
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27 | from target. The created string four-momentum will be equal total reaction |
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28 | four-momentum since annihilated system has small neglected momentum (only |
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29 | low momenta quarks are able to annihilate). |
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30 | |
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31 | To determine statistical weights for |
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32 | quark annihilation processes are leading to a string production |
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33 | and separate them from processes, when two or more strings can be produced we |
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34 | use the Regge motivated total cross section parametrization suggested by |
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35 | Donnachie and Landshoff \cite{DL92}. Using their parametrization the |
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36 | statistical weight for the one string production process is given by |
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37 | \begin{equation} |
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38 | \label{OSE1} W_{1} = \frac{Y_{hN}s^{-\eta}}{\sigma^{tot}_{hN}(s)} |
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39 | \end{equation} |
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40 | and statistical weight to produce two and more strings is given by |
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41 | \begin{equation} |
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42 | \label{OSE2} W_{2} = \frac{X_{hN}s^{\epsilon}}{\sigma^{tot}_{hN}(s)}, |
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43 | \end{equation} |
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44 | where hadron-nucleon total cross sections $\sigma^{tot}_{hN}(s)$ and its |
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45 | fit parameters $Y_{hN}$, $X_{hN}$, which do not depend |
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46 | from the total c.m. energy squared $s$ and depend on type of |
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47 | projectile hadron $h$ and target nucleon $N$ can be found in \cite{PDG96}. |
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48 | The reggeon intercept $\eta \approx |
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49 | 0.45$ and the pomeron intercept $\epsilon \approx 0.08$. |
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