Resonance scan

by nakulphy
Tags: breit wigner, resonance, scan
 P: 10 what is breit wigner distribution function ? it is used in resonance scan means it decides the no of events for any specific channel. i am also giving the link of the paper where i found this http://pos.sissa.it/archive/conferen...io2012_018.pdf please help me out thank you
 P: 305 The Breit-Wigner distribution is a particular factor appearing in the expression for the scattering cross section when this scattering happens via an intermediate particle. Consider for example the scattering $a+b\to A\to X+Y$. The expression for the cross section is given by: $$\frac{d\sigma(a+b\to X+Y)}{d\vec pd s_X}=\frac{d\Gamma(A\to X)}{\Gamma(A\to all)}\frac{d\sigma(a+b\to A+Y)}{d\vec pd s_A} W(s_A)\sqrt{\frac{\vec p^2+m_A^2}{\vec p^2+s_A}},$$ where the Breit-Wigner distribution is given by: $$W(s_A)=\frac{1}{\pi}\frac{m_A\Gamma}{(s_A-m_A^2)^2+m_A^2\Gamma^2}.$$ As you can see, such a distribution gives an enhancement of the cross section (i.e. of the number of particles produced) when $s_A\simeq m_A^2$, provided that the width $\Gamma$ of the intermediate particle is not too large.
 P: 10 thank you very much i will try to understand this and also try to correlate with the paper and will come back to you soon. thank you
 P: 305 Resonance scan The paper itself is about the exotic hadron X(3872). It is a perfect example of resonance. Namely it doesn't appear as a final state of the reaction but as an intermediate particle. It is, for example, produced ad LHC via the reaction: p+p -> X(3872) -> D0 + antiD0*. As you can see this is exactly as the reaction I showed you before.
 P: 10 thank you very much. can you please suggest me the reference book to study this ? actually I understood the things but still I want to understand in more detail. thank you Nakul Soni
 P: 305 Do you mean the X(3872) or resonances in general?
 P: 10 for the basic of Breit-Wigner and the distribution function.
 P: 305 One of the best books is De Wit - Field theory in particle physics. In particular the chapter on decay rates

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