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3<title>Diffraction</title>
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29
30<h2>Diffraction</h2>
31
32<h3>Introduction</h3>
33
34Diffraction is not well understood, and several alternative approaches
35have been proposed. Here we follow a fairly conventional Pomeron-based
36one, in the Ingelman-Schlein spirit [<a href="Bibliography.php" target="page">Ing85</a>],
37but integrated to make full use of the standard PYTHIA machinery
38for multiparton interactions, parton showers and hadronization
39[<a href="Bibliography.php" target="page">Nav10,Cor10a</a>]. This is the approach pioneered in the PomPyt
40program by Ingelman and collaborators [<a href="Bibliography.php" target="page">Ing97</a>].
41
42<p/>
43For ease of use (and of modelling), the Pomeron-specific parts of the
44generation are subdivided into three sets of parameters that are rather
45independent of each other:
46<br/>(i) the total, elastic and diffractive cross sections are
47parametrized as functions of the CM energy, or can be set by the user
48to the desired values, see the
49<?php $filepath = $_GET["filepath"];
50echo "<a href='TotalCrossSections.php?filepath=".$filepath."' target='page'>";?>Total Cross Sections</a> page;
51<br/>(ii) once it has been decided to have a diffractive process,
52a Pomeron flux parametrization is used to pick the mass of the
53diffractive system(s) and the <i>t</i> of the exchanged Pomeron,
54see below;
55<br/>(iii) a diffractive system of a given mass is classified either
56as low-mass unresolved, which gives a simple low-<i>pT</i> string
57topology, or as high-mass resolved, for which the full machinery of
58multiparton interactions and parton showers are applied, making use of
59<?php $filepath = $_GET["filepath"];
60echo "<a href='PDFSelection.php?filepath=".$filepath."' target='page'>";?>Pomeron PDFs</a>.
61<br/>The parameters related to multiparton interactions, parton showers
62and hadronization are kept the same as for normal nondiffractive events,
63with only one exception. This may be questioned, especially for the
64multiparton interactions, but we do not believe that there are currently
65enough good diffractive data that would allow detailed separate tunes.
66 
67<p/>
68The above subdivision may not represent the way "physics comes about".
69For instance, the total diffractive cross section can be viewed as a
70convolution of a Pomeron flux with a Pomeron-proton total cross section.
71Since neither of the two is known from first principles there will be
72a significant amount of ambiguity in the flux factor. The picture is
73further complicated by the fact that the possibility of simultaneous
74further multiparton interactions ("cut Pomerons") will screen the rate of
75diffractive systems. In the end, our set of parameters refers to the
76effective description that emerges out of these effects, rather than
77to the underlying "bare" parameters. 
78 
79<p/>
80In the event record the diffractive system in the case of an excited
81proton is denoted <code>p_diffr</code>, code 9902210, whereas
82a central diffractive system is denoted <code>rho_diffr</code>,
83code 9900110. Apart from representing the correct charge and baryon
84numbers, no deeper meaning should be attributed to the names.
85
86<h3>Pomeron flux</h3>
87
88As already mentioned above, the total diffractive cross section is fixed
89by a default energy-dependent parametrization or by the user, see the
90<?php $filepath = $_GET["filepath"];
91echo "<a href='TotalCrossSections.php?filepath=".$filepath."' target='page'>";?>Total Cross Sections</a> page.
92Therefore we do not attribute any significance to the absolute
93normalization of the Pomeron flux. The choice of Pomeron flux model
94still will decide on the mass spectrum of diffractive states and the
95<i>t</i> spectrum of the Pomeron exchange.
96
97<br/><br/><table><tr><td><strong>Diffraction:PomFlux </td><td>  &nbsp;&nbsp;(<code>default = <strong>1</strong></code>; <code>minimum = 1</code>; <code>maximum = 5</code>)</td></tr></table>
98Parametrization of the Pomeron flux <ei>f_Pom/p( x_Pom, t)</ei>.
99<br/>
100<input type="radio" name="1" value="1" checked="checked"><strong>1 </strong>: Schuler and Sj&ouml;strand <ref>Sch94</ref>: based on a critical Pomeron, giving a mass spectrum roughly like <ei>dm^2/m^2</ei>; a mass-dependent exponential <ei>t</ei> slope that reduces the rate  of low-mass states; partly compensated by a very-low-mass (resonance region)  enhancement. Is currently the only one that contains a separate  <ei>t</ei> spectrum for double diffraction (along with MBR) and  separate parameters for pion beams.<br/>
101<input type="radio" name="1" value="2"><strong>2 </strong>: Bruni and Ingelman <ref>Bru93</ref>: also a critical Pomeron giving close to <ei>dm^2/m^2</ei>, with a <ei>t</ei> distribution  the sum of two exponentials. The original model only covers single diffraction, but is here expanded by analogy to double and central  diffraction.<br/>
102<input type="radio" name="1" value="3"><strong>3 </strong>: a conventional Pomeron description, in the RapGap manual <ref>Jun95</ref> attributed to Berger et al. and Streng  <ref>Ber87a</ref>, but there (and here) with values updated to a  supercritical Pomeron with <ei>epsilon &gt; 0</ei> (see below),  which gives a stronger peaking towards low-mass diffractive states,  and with a mass-dependent (the <ei>alpha'</ei> below) exponential  <ei>t</ei> slope. The original model only covers single diffraction,  but is here expanded by analogy to double and central diffraction. <br/>
103<input type="radio" name="1" value="4"><strong>4 </strong>: a conventional Pomeron description, attributed to Donnachie and Landshoff <ref>Don84</ref>, again with supercritical Pomeron, with the same two parameters as option 3 above, but this time with a power-law <ei>t</ei> distribution. The original model only covers single diffraction, but is here expanded by analogy to double and central  diffraction.<br/>
104<input type="radio" name="1" value="5"><strong>5 </strong>: the MBR (Minimum Bias Rockefeller) simulation of (anti)proton-proton interactions <ref>Cie12</ref>. The event generation follows a renormalized-Regge-theory model, sucessfully tested using CDF data. The simulation includes single and double diffraction, as well as the central diffractive (double-Pomeron exchange) process (106). Only <ei>p p</ei>, <ei>pbar p</ei> and <ei>p pbar</ei> beam combinations  are allowed for this option. Several parameters of this model are listed  below. <br/>
105
106<p/>
107In options 3 and 4 above, the Pomeron Regge trajectory is
108parametrized as
109<br/><i>
110alpha(t) = 1 + epsilon + alpha' t
111</i><br/>
112The <i>epsilon</i> and <i>alpha'</i> parameters can be set
113separately:
114
115<br/><br/><table><tr><td><strong>Diffraction:PomFluxEpsilon </td><td></td><td> <input type="text" name="2" value="0.085" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.085</strong></code>; <code>minimum = 0.02</code>; <code>maximum = 0.15</code>)</td></tr></table>
116The Pomeron trajectory intercept <i>epsilon</i> above. For technical
117reasons <i>epsilon &gt; 0</i> is necessary in the current implementation.
118
119<br/><br/><table><tr><td><strong>Diffraction:PomFluxAlphaPrime </td><td></td><td> <input type="text" name="3" value="0.25" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.25</strong></code>; <code>minimum = 0.1</code>; <code>maximum = 0.4</code>)</td></tr></table>
120The Pomeron trajectory slope <i>alpha'</i> above.
121
122<p/>
123When option 5 is selected, the following parameters of the MBR model
124[<a href="Bibliography.php" target="page">Cie12</a>] are used:
125
126<br/><br/><table><tr><td><strong>Diffraction:MBRepsilon </td><td></td><td> <input type="text" name="4" value="0.104" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.104</strong></code>; <code>minimum = 0.02</code>; <code>maximum = 0.15</code>)</td></tr></table>
127<br/><br/><table><tr><td><strong>Diffraction:MBRalpha </td><td></td><td> <input type="text" name="5" value="0.25" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.25</strong></code>; <code>minimum = 0.1</code>; <code>maximum = 0.4</code>)</td></tr></table>
128the parameters of the Pomeron trajectory.
129
130<br/><br/><table><tr><td><strong>Diffraction:MBRbeta0 </td><td></td><td> <input type="text" name="6" value="6.566" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>6.566</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 10.0</code>)</td></tr></table>
131<br/><br/><table><tr><td><strong>Diffraction:MBRsigma0 </td><td></td><td> <input type="text" name="7" value="2.82" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.82</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
132the Pomeron-proton coupling, and the total Pomeron-proton cross section.
133
134<br/><br/><table><tr><td><strong>Diffraction:MBRm2Min </td><td></td><td> <input type="text" name="8" value="1.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.5</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 3.0</code>)</td></tr></table>
135the lowest value of the mass squared of the dissociated system.
136
137<br/><br/><table><tr><td><strong>Diffraction:MBRdyminSDflux </td><td></td><td> <input type="text" name="9" value="2.3" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.3</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
138<br/><br/><table><tr><td><strong>Diffraction:MBRdyminDDflux </td><td></td><td> <input type="text" name="10" value="2.3" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.3</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
139<br/><br/><table><tr><td><strong>Diffraction:MBRdyminCDflux </td><td></td><td> <input type="text" name="11" value="2.3" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.3</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
140the minimum width of the rapidity gap used in the calculation of
141<i>Ngap(s)</i> (flux renormalization).
142
143<br/><br/><table><tr><td><strong>Diffraction:MBRdyminSD </td><td></td><td> <input type="text" name="12" value="2.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.0</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
144<br/><br/><table><tr><td><strong>Diffraction:MBRdyminDD </td><td></td><td> <input type="text" name="13" value="2.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.0</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
145<br/><br/><table><tr><td><strong>Diffraction:MBRdyminCD </td><td></td><td> <input type="text" name="14" value="2.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.0</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 5.0</code>)</td></tr></table>
146the minimum width of the rapidity gap used in the calculation of cross
147sections, i.e. the parameter <i>dy_S</i>, which suppresses the cross
148section at low <i>dy</i> (non-diffractive region).
149
150<br/><br/><table><tr><td><strong>Diffraction:MBRdyminSigSD </td><td></td><td> <input type="text" name="15" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.001</code>; <code>maximum = 5.0</code>)</td></tr></table>
151<br/><br/><table><tr><td><strong>Diffraction:MBRdyminSigDD </td><td></td><td> <input type="text" name="16" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.001</code>; <code>maximum = 5.0</code>)</td></tr></table>
152<br/><br/><table><tr><td><strong>Diffraction:MBRdyminSigCD </td><td></td><td> <input type="text" name="17" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.001</code>; <code>maximum = 5.0</code>)</td></tr></table>
153the parameter <i>sigma_S</i>, used for the cross section suppression at
154low <i>dy</i> (non-diffractive region).
155
156<h3>Separation into low and high masses</h3>
157
158Preferably one would want to have a perturbative picture of the
159dynamics of Pomeron-proton collisions, like multiparton interactions
160provide for proton-proton ones. However, while PYTHIA by default
161will only allow collisions with a CM energy above 10 GeV, the
162mass spectrum of diffractive systems will stretch to down to
163the order of 1.2 GeV. It would not be feasible to attempt a
164perturbative description there. Therefore we do offer a simpler
165low-mass description, with only longitudinally stretched strings,
166with a gradual switch-over to the perturbative picture for higher
167masses. The probability for the latter picture is parametrized as
168<br/><i>
169P_pert = P_max ( 1 - exp( (m_diffr - m_min) / m_width ) )
170</i><br/>
171which vanishes for the diffractive system mass
172<i>m_diffr &lt; m_min</i>, and is <i>1 - 1/e = 0.632</i> for
173<i>m_diffr = m_min + m_width</i>, assuming <i>P_max = 1</i>.
174
175<br/><br/><table><tr><td><strong>Diffraction:mMinPert </td><td></td><td> <input type="text" name="18" value="10." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>10.</strong></code>; <code>minimum = 5.</code>)</td></tr></table>
176The abovementioned threshold mass <i>m_min</i> for phasing in a
177perturbative treatment. If you put this parameter to be bigger than
178the CM energy then there will be no perturbative description at all,
179but only the older low-<i>pt</i> description.
180 
181
182<br/><br/><table><tr><td><strong>Diffraction:mWidthPert </td><td></td><td> <input type="text" name="19" value="10." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>10.</strong></code>; <code>minimum = 0.</code>)</td></tr></table>
183The abovementioned threshold width <i>m_width.</i>
184 
185
186<br/><br/><table><tr><td><strong>Diffraction:probMaxPert </td><td></td><td> <input type="text" name="20" value="1." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.</strong></code>; <code>minimum = 0.</code>; <code>maximum = 1.</code>)</td></tr></table>
187The abovementioned maximum probability <i>P_max.</i>. Would
188normally be assumed to be unity, but a somewhat lower value could
189be used to represent a small nonperturbative component also at
190high diffractive masses.
191 
192
193<h3>Low-mass diffraction</h3>
194
195When an incoming hadron beam is diffractively excited, it is modeled
196as if either a valence quark or a gluon is kicked out from the hadron.
197In the former case this produces a simple string to the leftover
198remnant, in the latter it gives a hairpin arrangement where a string
199is stretched from one quark in the remnant, via the gluon, back to the   
200rest of the remnant. The latter ought to dominate at higher mass of
201the diffractive system. Therefore an approximate behaviour like
202<br/><i>
203P_q / P_g = N / m^p
204</i><br/>
205is assumed.
206
207<br/><br/><table><tr><td><strong>Diffraction:pickQuarkNorm </td><td></td><td> <input type="text" name="21" value="5.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>5.0</strong></code>; <code>minimum = 0.</code>)</td></tr></table>
208The abovementioned normalization <i>N</i> for the relative quark
209rate in diffractive systems.
210 
211
212<br/><br/><table><tr><td><strong>Diffraction:pickQuarkPower </td><td></td><td> <input type="text" name="22" value="1.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.0</strong></code>)</td></tr></table>
213The abovementioned mass-dependence power <i>p</i> for the relative
214quark rate in diffractive systems.
215 
216
217<p/>
218When a gluon is kicked out from the hadron, the longitudinal momentum
219sharing between the the two remnant partons is determined by the
220same parameters as above. It is plausible that the primordial
221<i>kT</i> may be lower than in perturbative processes, however:
222
223<br/><br/><table><tr><td><strong>Diffraction:primKTwidth </td><td></td><td> <input type="text" name="23" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.</code>)</td></tr></table>
224The width of Gaussian distributions in <i>p_x</i> and <i>p_y</i>
225separately that is assigned as a primordial <i>kT</i> to the two
226beam remnants when a gluon is kicked out of a diffractive system.
227 
228
229<br/><br/><table><tr><td><strong>Diffraction:largeMassSuppress </td><td></td><td> <input type="text" name="24" value="2." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>2.</strong></code>; <code>minimum = 0.</code>)</td></tr></table>
230The choice of longitudinal and transverse structure of a diffractive
231beam remnant for a kicked-out gluon implies a remnant mass
232<i>m_rem</i> distribution (i.e. quark plus diquark invariant mass
233for a baryon beam) that knows no bounds. A suppression like
234<i>(1 - m_rem^2 / m_diff^2)^p</i> is therefore introduced, where
235<i>p</i> is the <code>diffLargeMassSuppress</code> parameter.   
236 
237
238<h3>High-mass diffraction</h3>
239
240The perturbative description need to use parton densities of the
241Pomeron. The options are described in the page on
242<?php $filepath = $_GET["filepath"];
243echo "<a href='PDFSelection.php?filepath=".$filepath."' target='page'>";?>PDF Selection</a>. The standard
244perturbative multiparton interactions framework then provides
245cross sections for parton-parton interactions. In order to
246turn these cross section into probabilities one also needs an
247ansatz for the Pomeron-proton total cross section. In the literature
248one often finds low numbers for this, of the order of 2 mb.
249These, if taken at face value, would give way too much activity
250per event. There are ways to tame this, e.g. by a larger <i>pT0</i>
251than in the normal pp framework. Actually, there are many reasons
252to use a completely different set of parameters for MPI in
253diffraction than in pp collisions, especially with respect to the
254impact-parameter picture, see below. A lower number in some frameworks
255could alternatively be regarded as a consequence of screening, with
256a larger "bare" number.   
257
258<p/>
259For now, however, an attempt at the most general solution would
260carry too far, and instead we patch up the problem by using a
261larger Pomeron-proton total cross section, such that average
262activity makes more sense. This should be viewed as the main
263tunable parameter in the description of high-mass diffraction.
264It is to be fitted to diffractive event-shape data such as the average
265charged multiplicity. It would be very closely tied to the choice of
266Pomeron PDF; we remind that some of these add up to less than unit
267momentum sum in the Pomeron, a choice that also affect the value
268one ends up with. Furthermore, like with hadronic cross sections,
269it is quite plausible that the Pomeron-proton cross section increases
270with energy, so we have allowed for a powerlike dependence on the
271diffractive mass.
272
273<br/><br/><table><tr><td><strong>Diffraction:sigmaRefPomP </td><td></td><td> <input type="text" name="25" value="10." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>10.</strong></code>; <code>minimum = 2.</code>; <code>maximum = 40.</code>)</td></tr></table>
274The assumed Pomeron-proton effective cross section, as used for
275multiparton interactions in diffractive systems. If this cross section
276is made to depend on the mass of the diffractive system then the above
277value refers to the cross section at the reference scale, and
278<br/><i>
279sigma_PomP(m) = sigma_PomP(m_ref) * (m / m_ref)^p 
280</i><br/>
281where <i>m</i> is the mass of the diffractive system, <i>m_ref</i>
282is the reference mass scale <code>Diffraction:mRefPomP</code> below and
283<i>p</i> is the mass-dependence power <code>Diffraction:mPowPomP</code>.
284Note that a larger cross section value gives less MPI activity per event.
285There is no point in making the cross section too big, however, since
286then <i>pT0</i> will be adjusted downwards to ensure that the
287integrated perturbative cross section stays above this assumed total
288cross section. (The requirement of at least one perturbative interaction
289per event.)
290 
291
292<br/><br/><table><tr><td><strong>Diffraction:mRefPomP </td><td></td><td> <input type="text" name="26" value="100.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>100.0</strong></code>; <code>minimum = 1.</code>)</td></tr></table>
293The <i>mRef</i> reference mass scale introduced above.
294 
295
296<br/><br/><table><tr><td><strong>Diffraction:mPowPomP </td><td></td><td> <input type="text" name="27" value="0.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.0</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 0.5</code>)</td></tr></table>
297The <i>p</i> mass rescaling pace introduced above.
298 
299
300<p/> 
301Also note that, even for a fixed CM energy of events, the diffractive
302subsystem will range from the abovementioned threshold mass
303<i>m_min</i> to the full CM energy, with a variation of parameters
304such as <i>pT0</i> along this mass range. Therefore multiparton
305interactions are initialized for a few different diffractive masses,
306currently five, and all relevant parameters are interpolated between
307them to obtain the behaviour at a specific diffractive mass.
308Furthermore, <i>A B -&gt;X B</i> and <i>A B -&gt;A X</i> are
309initialized separately, to allow for different beams or PDF's on the
310two sides. These two aspects mean that initialization of MPI is
311appreciably slower when perturbative high-mass diffraction is allowed.
312
313<p/> 
314Diffraction tends to be peripheral, i.e. occur at intermediate impact
315parameter for the two protons. That aspect is implicit in the selection
316of diffractive cross section. For the simulation of the Pomeron-proton
317subcollision it is the impact-parameter distribution of that particular
318subsystem that should rather be modelled. That is, it also involves
319the transverse coordinate space of a Pomeron wavefunction. The outcome
320of the convolution therefore could be a different shape than for
321nondiffractive events. For simplicity we allow the same kind of
322options as for nondiffractive events, except that the
323<code>bProfile = 4</code> option for now is not implemented.
324
325<br/><br/><table><tr><td><strong>Diffraction:bProfile </td><td>  &nbsp;&nbsp;(<code>default = <strong>1</strong></code>; <code>minimum = 0</code>; <code>maximum = 3</code>)</td></tr></table>
326Choice of impact parameter profile for the incoming hadron beams.
327<br/>
328<input type="radio" name="28" value="0"><strong>0 </strong>: no impact parameter dependence at all.<br/>
329<input type="radio" name="28" value="1" checked="checked"><strong>1 </strong>: a simple Gaussian matter distribution;  no free parameters.<br/>
330<input type="radio" name="28" value="2"><strong>2 </strong>: a double Gaussian matter distribution, with the two free parameters <ei>coreRadius</ei> and  <ei>coreFraction</ei>.<br/>
331<input type="radio" name="28" value="3"><strong>3 </strong>: an overlap function, i.e. the convolution of the matter distributions of the two incoming hadrons, of the form <ei>exp(- b^expPow)</ei>, where <ei>expPow</ei> is a free  parameter.<br/>
332
333<br/><br/><table><tr><td><strong>Diffraction:coreRadius </td><td></td><td> <input type="text" name="29" value="0.4" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.4</strong></code>; <code>minimum = 0.1</code>; <code>maximum = 1.</code>)</td></tr></table>
334When assuming a double Gaussian matter profile, <i>bProfile = 2</i>,
335the inner core is assumed to have a radius that is a factor
336<i>coreRadius</i> smaller than the rest.
337   
338
339<br/><br/><table><tr><td><strong>Diffraction:coreFraction </td><td></td><td> <input type="text" name="30" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.</code>; <code>maximum = 1.</code>)</td></tr></table>
340When assuming a double Gaussian matter profile, <i>bProfile = 2</i>,
341the inner core is assumed to have a fraction <i>coreFraction</i>
342of the matter content of the hadron.
343   
344
345<br/><br/><table><tr><td><strong>Diffraction:expPow </td><td></td><td> <input type="text" name="31" value="1." size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.</strong></code>; <code>minimum = 0.4</code>; <code>maximum = 10.</code>)</td></tr></table>
346When <i>bProfile = 3</i> it gives the power of the assumed overlap
347shape <i>exp(- b^expPow)</i>. Default corresponds to a simple
348exponential drop, which is not too dissimilar from the overlap
349obtained with the standard double Gaussian parameters. For
350<i>expPow = 2</i> we reduce to the simple Gaussian, <i>bProfile = 1</i>,
351and for <i>expPow -> infinity</i> to no impact parameter dependence
352at all, <i>bProfile = 0</i>. For small <i>expPow</i> the program
353becomes slow and unstable, so the min limit must be respected.
354   
355
356<input type="hidden" name="saved" value="1"/>
357
358<?php
359echo "<input type='hidden' name='filepath' value='".$_GET["filepath"]."'/>"?>
360
361<table width="100%"><tr><td align="right"><input type="submit" value="Save Settings" /></td></tr></table>
362</form>
363
364<?php
365
366if($_POST["saved"] == 1)
367{
368$filepath = $_POST["filepath"];
369$handle = fopen($filepath, 'a');
370
371if($_POST["1"] != "1")
372{
373$data = "Diffraction:PomFlux = ".$_POST["1"]."\n";
374fwrite($handle,$data);
375}
376if($_POST["2"] != "0.085")
377{
378$data = "Diffraction:PomFluxEpsilon = ".$_POST["2"]."\n";
379fwrite($handle,$data);
380}
381if($_POST["3"] != "0.25")
382{
383$data = "Diffraction:PomFluxAlphaPrime = ".$_POST["3"]."\n";
384fwrite($handle,$data);
385}
386if($_POST["4"] != "0.104")
387{
388$data = "Diffraction:MBRepsilon = ".$_POST["4"]."\n";
389fwrite($handle,$data);
390}
391if($_POST["5"] != "0.25")
392{
393$data = "Diffraction:MBRalpha = ".$_POST["5"]."\n";
394fwrite($handle,$data);
395}
396if($_POST["6"] != "6.566")
397{
398$data = "Diffraction:MBRbeta0 = ".$_POST["6"]."\n";
399fwrite($handle,$data);
400}
401if($_POST["7"] != "2.82")
402{
403$data = "Diffraction:MBRsigma0 = ".$_POST["7"]."\n";
404fwrite($handle,$data);
405}
406if($_POST["8"] != "1.5")
407{
408$data = "Diffraction:MBRm2Min = ".$_POST["8"]."\n";
409fwrite($handle,$data);
410}
411if($_POST["9"] != "2.3")
412{
413$data = "Diffraction:MBRdyminSDflux = ".$_POST["9"]."\n";
414fwrite($handle,$data);
415}
416if($_POST["10"] != "2.3")
417{
418$data = "Diffraction:MBRdyminDDflux = ".$_POST["10"]."\n";
419fwrite($handle,$data);
420}
421if($_POST["11"] != "2.3")
422{
423$data = "Diffraction:MBRdyminCDflux = ".$_POST["11"]."\n";
424fwrite($handle,$data);
425}
426if($_POST["12"] != "2.0")
427{
428$data = "Diffraction:MBRdyminSD = ".$_POST["12"]."\n";
429fwrite($handle,$data);
430}
431if($_POST["13"] != "2.0")
432{
433$data = "Diffraction:MBRdyminDD = ".$_POST["13"]."\n";
434fwrite($handle,$data);
435}
436if($_POST["14"] != "2.0")
437{
438$data = "Diffraction:MBRdyminCD = ".$_POST["14"]."\n";
439fwrite($handle,$data);
440}
441if($_POST["15"] != "0.5")
442{
443$data = "Diffraction:MBRdyminSigSD = ".$_POST["15"]."\n";
444fwrite($handle,$data);
445}
446if($_POST["16"] != "0.5")
447{
448$data = "Diffraction:MBRdyminSigDD = ".$_POST["16"]."\n";
449fwrite($handle,$data);
450}
451if($_POST["17"] != "0.5")
452{
453$data = "Diffraction:MBRdyminSigCD = ".$_POST["17"]."\n";
454fwrite($handle,$data);
455}
456if($_POST["18"] != "10.")
457{
458$data = "Diffraction:mMinPert = ".$_POST["18"]."\n";
459fwrite($handle,$data);
460}
461if($_POST["19"] != "10.")
462{
463$data = "Diffraction:mWidthPert = ".$_POST["19"]."\n";
464fwrite($handle,$data);
465}
466if($_POST["20"] != "1.")
467{
468$data = "Diffraction:probMaxPert = ".$_POST["20"]."\n";
469fwrite($handle,$data);
470}
471if($_POST["21"] != "5.0")
472{
473$data = "Diffraction:pickQuarkNorm = ".$_POST["21"]."\n";
474fwrite($handle,$data);
475}
476if($_POST["22"] != "1.0")
477{
478$data = "Diffraction:pickQuarkPower = ".$_POST["22"]."\n";
479fwrite($handle,$data);
480}
481if($_POST["23"] != "0.5")
482{
483$data = "Diffraction:primKTwidth = ".$_POST["23"]."\n";
484fwrite($handle,$data);
485}
486if($_POST["24"] != "2.")
487{
488$data = "Diffraction:largeMassSuppress = ".$_POST["24"]."\n";
489fwrite($handle,$data);
490}
491if($_POST["25"] != "10.")
492{
493$data = "Diffraction:sigmaRefPomP = ".$_POST["25"]."\n";
494fwrite($handle,$data);
495}
496if($_POST["26"] != "100.0")
497{
498$data = "Diffraction:mRefPomP = ".$_POST["26"]."\n";
499fwrite($handle,$data);
500}
501if($_POST["27"] != "0.0")
502{
503$data = "Diffraction:mPowPomP = ".$_POST["27"]."\n";
504fwrite($handle,$data);
505}
506if($_POST["28"] != "1")
507{
508$data = "Diffraction:bProfile = ".$_POST["28"]."\n";
509fwrite($handle,$data);
510}
511if($_POST["29"] != "0.4")
512{
513$data = "Diffraction:coreRadius = ".$_POST["29"]."\n";
514fwrite($handle,$data);
515}
516if($_POST["30"] != "0.5")
517{
518$data = "Diffraction:coreFraction = ".$_POST["30"]."\n";
519fwrite($handle,$data);
520}
521if($_POST["31"] != "1.")
522{
523$data = "Diffraction:expPow = ".$_POST["31"]."\n";
524fwrite($handle,$data);
525}
526fclose($handle);
527}
528
529?>
530</body>
531</html>
532
533<!-- Copyright (C) 2012 Torbjorn Sjostrand -->
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