[1] | 1 | <chapter name="Onia Processes"> |
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| 2 | |
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| 3 | <h2>Onia Processes</h2> |
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| 4 | |
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| 5 | Production of J/psi or Upsilon, directly and via chi states and the |
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| 6 | colour-octet mechanism. |
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| 7 | In each process the square-bracketed expression specifies the state |
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| 8 | in spectroscopic notation, <ei>(2S+1) L J</ei>, followed by |
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| 9 | <ei>(1)</ei> for colour-singlet states and <ei>(8)</ei> for |
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| 10 | colour-octet ditto. |
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| 11 | |
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| 12 | <p/> |
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| 13 | The original Fortran code for these processes has been contributed |
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| 14 | by Stefan Wolf [unpublished]. For the C++ version only the unpolarized |
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| 15 | expressions are retained, since the theoretical predictions of the |
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| 16 | colour-octet model anyway do not agree with the experimental |
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| 17 | observations. Furthermore, the polarization effects are modest, |
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| 18 | so isotropic decay is not a bad starting point. Such an event sample |
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| 19 | can afterwards be reweighted at will by the user, to test various |
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| 20 | assumptions. |
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| 21 | |
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| 22 | <p/> |
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| 23 | The description of |
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| 24 | <aloc href="TimelikeShowers">final-state radiation</aloc> |
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| 25 | is in this case based on some further model assumptions. |
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| 26 | |
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| 27 | <p/> |
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| 28 | Most of the processes below are divergent in the limit <ei>pT -> 0</ei>, |
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| 29 | and therefore a <ei>pTmin</ei> scale should be set. Comparisons with |
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| 30 | data indicate that this divergence can be tamed the same way as for |
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| 31 | the normal QCD <ei>2 -> 2</ei> cross sections <ref>Bar06,Kra08</ref>, |
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| 32 | which makes sense, since they are all dominated by the same kind of |
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| 33 | <ei>t</ei>-channel gluon exchange. It is therefore possible to use the |
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| 34 | <aloc href="UserHooks">SuppressSmallPT</aloc> user hook to impose a |
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| 35 | reweighting that cancels the low-<ei>pT</ei> divergence. |
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| 36 | |
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| 37 | <p/> |
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| 38 | An eikonalized description of these processes is included in the |
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| 39 | multiparton-interactions framework. Here the low-<ei>pT</ei> dampening |
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| 40 | is automatic, and additionally the framework is more consistent |
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| 41 | (e.g. with respect to energy-momentum constraints and the |
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| 42 | impact-parameter description) for events where the onium production |
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| 43 | is not the hardest subprocess, as would often be the case in the |
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| 44 | low-<ei>pT</ei> limit. |
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| 45 | |
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| 46 | <h3>Charmonium</h3> |
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| 47 | |
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| 48 | <flag name="Charmonium:all" default="off"> |
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| 49 | Common switch for the group of charmonium production. |
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| 50 | </flag> |
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| 51 | |
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| 52 | <flag name="Charmonium:gg2QQbar[3S1(1)]g" default="off"> |
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| 53 | <ei>g g -> ccbar[3S1(1)] g</ei>. |
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| 54 | Code 401. |
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| 55 | </flag> |
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| 56 | |
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| 57 | <flag name="Charmonium:gg2QQbar[3P0(1)]g" default="off"> |
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| 58 | <ei>g g -> ccbar[3P0(1)] g</ei>. |
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| 59 | Code 402. |
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| 60 | </flag> |
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| 61 | |
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| 62 | <flag name="Charmonium:gg2QQbar[3P1(1)]g" default="off"> |
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| 63 | <ei>g g -> ccbar[3P1(1)] g</ei>. |
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| 64 | Code 403. |
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| 65 | </flag> |
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| 66 | |
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| 67 | <flag name="Charmonium:gg2QQbar[3P2(1)]g" default="off"> |
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| 68 | <ei>g g -> ccbar[3P2(1)] g</ei>. |
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| 69 | Code 404. |
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| 70 | </flag> |
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| 71 | |
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| 72 | <flag name="Charmonium:qg2QQbar[3P0(1)]q" default="off"> |
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| 73 | <ei>q g -> ccbar[3P0(1)] q</ei>. |
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| 74 | Code 405. |
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| 75 | </flag> |
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| 76 | |
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| 77 | <flag name="Charmonium:qg2QQbar[3P1(1)]q" default="off"> |
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| 78 | <ei>q g -> ccbar[3P1(1)] q</ei>. |
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| 79 | Code 406. |
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| 80 | </flag> |
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| 81 | |
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| 82 | <flag name="Charmonium:qg2QQbar[3P2(1)]q" default="off"> |
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| 83 | <ei>q g -> ccbar[3P2(1)] q</ei>. |
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| 84 | Code 407. |
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| 85 | </flag> |
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| 86 | |
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| 87 | <flag name="Charmonium:qqbar2QQbar[3P0(1)]g" default="off"> |
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| 88 | <ei>q qbar -> ccbar[3P0(1)] g</ei>. |
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| 89 | Code 408. |
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| 90 | </flag> |
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| 91 | |
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| 92 | <flag name="Charmonium:qqbar2QQbar[3P1(1)]g" default="off"> |
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| 93 | <ei>q qbar -> ccbar[3P1(1)] g</ei>. |
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| 94 | Code 409. |
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| 95 | </flag> |
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| 96 | |
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| 97 | <flag name="Charmonium:qqbar2QQbar[3P2(1)]g" default="off"> |
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| 98 | <ei>q qbar -> ccbar[3P2(1)] g</ei>. |
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| 99 | Code 410. |
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| 100 | </flag> |
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| 101 | |
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| 102 | <flag name="Charmonium:gg2QQbar[3S1(8)]g" default="off"> |
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| 103 | <ei>g g -> ccbar[3S1(8)] g</ei>. |
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| 104 | Code 411. |
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| 105 | </flag> |
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| 106 | |
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| 107 | <flag name="Charmonium:gg2QQbar[1S0(8)]g" default="off"> |
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| 108 | <ei>g g -> ccbar[3S1(8)] g</ei>. |
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| 109 | Code 412. |
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| 110 | </flag> |
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| 111 | |
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| 112 | <flag name="Charmonium:gg2QQbar[3PJ(8)]g" default="off"> |
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| 113 | <ei>g g -> ccbar[3S1(8)] g</ei>. |
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| 114 | Code 413. |
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| 115 | </flag> |
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| 116 | |
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| 117 | <flag name="Charmonium:qg2QQbar[3S1(8)]q" default="off"> |
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| 118 | <ei>q g -> ccbar[3S1(8)] q</ei>. |
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| 119 | Code 414. |
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| 120 | </flag> |
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| 121 | |
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| 122 | <flag name="Charmonium:qg2QQbar[1S0(8)]q" default="off"> |
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| 123 | <ei>q g -> ccbar[3S1(8)] q</ei>. |
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| 124 | Code 415. |
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| 125 | </flag> |
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| 126 | |
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| 127 | <flag name="Charmonium:qg2QQbar[3PJ(8)]q" default="off"> |
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| 128 | <ei>q g -> ccbar[3S1(8)] q</ei>. |
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| 129 | Code 416. |
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| 130 | </flag> |
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| 131 | |
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| 132 | <flag name="Charmonium:qqbar2QQbar[3S1(8)]g" default="off"> |
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| 133 | <ei>q qbar -> ccbar[3S1(8)] g</ei>. |
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| 134 | Code 417. |
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| 135 | </flag> |
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| 136 | |
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| 137 | <flag name="Charmonium:qqbar2QQbar[1S0(8)]g" default="off"> |
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| 138 | <ei>q qbar -> ccbar[3S1(8)] g</ei>. |
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| 139 | Code 418. |
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| 140 | </flag> |
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| 141 | |
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| 142 | <flag name="Charmonium:qqbar2QQbar[3PJ(8)]g" default="off"> |
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| 143 | <ei>q qbar -> ccbar[3S1(8)] g</ei>. |
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| 144 | Code 419. |
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| 145 | </flag> |
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| 146 | |
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| 147 | <h3>Bottomonium</h3> |
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| 148 | |
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| 149 | <flag name="Bottomonium:all" default="off"> |
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| 150 | Common switch for the group of charmonium production. |
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| 151 | </flag> |
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| 152 | |
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| 153 | <flag name="Bottomonium:gg2QQbar[3S1(1)]g" default="off"> |
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| 154 | <ei>g g -> bbbar[3S1(1)] g</ei>. |
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| 155 | Code 501. |
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| 156 | </flag> |
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| 157 | |
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| 158 | <flag name="Bottomonium:gg2QQbar[3P0(1)]g" default="off"> |
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| 159 | <ei>g g -> bbbar[3P0(1)] g</ei>. |
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| 160 | Code 502. |
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| 161 | </flag> |
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| 162 | |
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| 163 | <flag name="Bottomonium:gg2QQbar[3P1(1)]g" default="off"> |
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| 164 | <ei>g g -> bbbar[3P1(1)] g</ei>. |
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| 165 | Code 503. |
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| 166 | </flag> |
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| 167 | |
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| 168 | <flag name="Bottomonium:gg2QQbar[3P2(1)]g" default="off"> |
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| 169 | <ei>g g -> bbbar[3P2(1)] g</ei>. |
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| 170 | Code 504. |
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| 171 | </flag> |
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| 172 | |
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| 173 | <flag name="Bottomonium:qg2QQbar[3P0(1)]q" default="off"> |
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| 174 | <ei>q g -> bbbar[3P0(1)] q</ei>. |
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| 175 | Code 505. |
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| 176 | </flag> |
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| 177 | |
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| 178 | <flag name="Bottomonium:qg2QQbar[3P1(1)]q" default="off"> |
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| 179 | <ei>q g -> bbbar[3P1(1)] q</ei>. |
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| 180 | Code 506. |
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| 181 | </flag> |
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| 182 | |
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| 183 | <flag name="Bottomonium:qg2QQbar[3P2(1)]q" default="off"> |
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| 184 | <ei>q g -> bbbar[3P2(1)] q</ei>. |
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| 185 | Code 507. |
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| 186 | </flag> |
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| 187 | |
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| 188 | <flag name="Bottomonium:qqbar2QQbar[3P0(1)]g" default="off"> |
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| 189 | <ei>q qbar -> bbbar[3P0(1)] g</ei>. |
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| 190 | Code 508. |
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| 191 | </flag> |
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| 192 | |
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| 193 | <flag name="Bottomonium:qqbar2QQbar[3P1(1)]g" default="off"> |
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| 194 | <ei>q qbar -> bbbar[3P1(1)] g</ei>. |
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| 195 | Code 509. |
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| 196 | </flag> |
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| 197 | |
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| 198 | <flag name="Bottomonium:qqbar2QQbar[3P2(1)]g" default="off"> |
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| 199 | <ei>q qbar -> bbbar[3P2(1)] g</ei>. |
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| 200 | Code 510. |
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| 201 | </flag> |
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| 202 | |
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| 203 | <flag name="Bottomonium:gg2QQbar[3S1(8)]g" default="off"> |
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| 204 | <ei>g g -> bbbar[3S1(8)] g</ei>. |
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| 205 | Code 511. |
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| 206 | </flag> |
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| 207 | |
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| 208 | <flag name="Bottomonium:gg2QQbar[1S0(8)]g" default="off"> |
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| 209 | <ei>g g -> bbbar[3S1(8)] g</ei>. |
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| 210 | Code 512. |
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| 211 | </flag> |
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| 212 | |
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| 213 | <flag name="Bottomonium:gg2QQbar[3PJ(8)]g" default="off"> |
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| 214 | <ei>g g -> bbbar[3S1(8)] g</ei>. |
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| 215 | Code 513. |
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| 216 | </flag> |
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| 217 | |
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| 218 | <flag name="Bottomonium:qg2QQbar[3S1(8)]q" default="off"> |
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| 219 | <ei>q g -> bbbar[3S1(8)] q</ei>. |
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| 220 | Code 514. |
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| 221 | </flag> |
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| 222 | |
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| 223 | <flag name="Bottomonium:qg2QQbar[1S0(8)]q" default="off"> |
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| 224 | <ei>q g -> bbbar[3S1(8)] q</ei>. |
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| 225 | Code 515. |
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| 226 | </flag> |
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| 227 | |
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| 228 | <flag name="Bottomonium:qg2QQbar[3PJ(8)]q" default="off"> |
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| 229 | <ei>q g -> bbbar[3S1(8)] q</ei>. |
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| 230 | Code 516. |
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| 231 | </flag> |
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| 232 | |
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| 233 | <flag name="Bottomonium:qqbar2QQbar[3S1(8)]g" default="off"> |
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| 234 | <ei>q qbar -> bbbar[3S1(8)] g</ei>. |
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| 235 | Code 517. |
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| 236 | </flag> |
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| 237 | |
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| 238 | <flag name="Bottomonium:qqbar2QQbar[1S0(8)]g" default="off"> |
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| 239 | <ei>q qbar -> bbbar[3S1(8)] g</ei>. |
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| 240 | Code 518. |
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| 241 | </flag> |
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| 242 | |
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| 243 | <flag name="Bottomonium:qqbar2QQbar[3PJ(8)]g" default="off"> |
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| 244 | <ei>q qbar -> bbbar[3S1(8)] g</ei>. |
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| 245 | Code 519. |
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| 246 | </flag> |
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| 247 | |
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| 248 | <h3>Onium matrix elements</h3> |
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| 249 | |
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| 250 | The implementation of charmonium and bottomonium production, including |
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| 251 | the colour-octet production mechanism, requires information on NRQCD |
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| 252 | matrix elements for the various wavefunctions involved. Default values |
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| 253 | for these are encoded in the following ten variables. They |
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| 254 | are taken from <ref>Nas00</ref>; see also <ref>Bar06</ref>. |
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| 255 | |
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| 256 | <parm name="Charmonium:OJpsi3S11" default="1.16" min="0.0"> |
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| 257 | <ei><O(J/psi)[3S1(1)]></ei>. |
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| 258 | </parm> |
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| 259 | |
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| 260 | <parm name="Charmonium:OJpsi3S18" default="0.0119" min="0.0"> |
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| 261 | <ei><O(J/psi)[3S1(8)]></ei>. |
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| 262 | </parm> |
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| 263 | |
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| 264 | <parm name="Charmonium:OJpsi1S08" default="0.01" min="0.0"> |
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| 265 | <ei><O(J/psi)[1S0(8)]></ei>. |
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| 266 | </parm> |
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| 267 | |
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| 268 | <parm name="Charmonium:OJpsi3P08" default="0.01" min="0.0"> |
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| 269 | <ei><O(J/psi)[3P0(8)]>/m_c^2</ei>. |
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| 270 | </parm> |
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| 271 | |
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| 272 | <parm name="Charmonium:Ochic03P01" default="0.05" min="0.0"> |
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| 273 | <ei><O(chi_c0)[3P0(8)]>/m_c^2</ei>. |
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| 274 | </parm> |
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| 275 | |
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| 276 | <parm name="Bottomonium:OUpsilon3S11" default="9.28" min="0.0"> |
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| 277 | <ei><O(Upsilon)[3S1(1)]></ei>. |
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| 278 | </parm> |
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| 279 | |
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| 280 | <parm name="Bottomonium:OUpsilon3S18" default="0.15" min="0.0"> |
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| 281 | <ei><O(Upsilon)[3S1(8)]></ei>. |
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| 282 | </parm> |
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| 283 | |
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| 284 | <parm name="Bottomonium:OUpsilon1S08" default="0.02" min="0.0"> |
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| 285 | <ei><O(Upsilon)[1S0(8)]></ei>. |
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| 286 | </parm> |
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| 287 | |
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| 288 | <parm name="Bottomonium:OUpsilon3P08" default="0.02" min="0.0"> |
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| 289 | <ei><O(Upsilon)[3P0(8)]>/m_b^2</ei>. |
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| 290 | </parm> |
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| 291 | |
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| 292 | <parm name="Bottomonium:Ochib03P01" default="0.085" min="0.0"> |
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| 293 | <ei><O(chi_b0)[3P0(8)]>/m_b^2</ei>. |
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| 294 | </parm> |
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| 295 | |
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| 296 | |
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| 297 | </chapter> |
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| 298 | |
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| 299 | <!-- Copyright (C) 2012 Torbjorn Sjostrand --> |
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| 300 | |
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