Godbole, Rohini M and Pancheri, G (2001) $\gamma \gamma$ crosssections and $\gamma \gamma$ colliders. [Preprint]

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Abstract
We summarize the predictions of different models for total $\gamma \gamma$ crosssections. The experimentaly observed rise of $\sigma_{\gamma \gamma}$ with $\sqrt{s_{\gamma \gamma}}$, faster than that for $\sigma_{\bar p p}$, $\sigma_{\gamma p}$ is in agreement with the predictions of the Eikonalized Minijet Models as opposed to those of the ReggePomeron models. We then show that a measurement of $\sigma_{\gamma \gamma}$ with an accuracy of $\lessapprox 89% (67%)$ is necessary to distinguish among different ReggePomeron type models (among the different parametrisations of the EMM models) and a precision of < lessapprox 20% is required to distinguish among the predictions of the EMMs and of those models which treat like 'photon like a proton', for the energy range $300 < \sqrt{s_{\gamma \gamma}} < 500$ GeV. We further show that the difference in model predictions for $\sigma_{\gamma \gamma}$ of about a factor 2 at $\sqrt{s_{\gamma \gamma}} = 700 $ GeV reduces to $\sim$ 30% when folded with bremsstrahlung $\gamma$ spectra to calculate $\sigma ({e^+e^ \to e^+e^\gamma \gamma \to e^+e^X})$. We point out then the special role that $\gamma \gamma$ colliders can play in shedding light on this allimportant issue of calculation of total hadronic crosssections.
Item Type:  Preprint 

Additional Information:  Nucl.Instrum.Meth. A472 (2001) 205211 
Department/Centre:  Division of Physical & Mathematical Sciences > Centre for Theoretical Studies (Ceased to exist at the end of 2003) 
Date Deposited:  13 Aug 2004 
Last Modified:  19 Sep 2010 04:13 
URI:  http://eprints.iisc.ac.in/id/eprint/815 
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