# Multiplicity Derivative: A new signature of first order phase transition in intermediate energy heavy ion collision

## TL;DR

This paper proposes that the derivative of total multiplicity with respect to excitation energy per nucleon can serve as a signature of first order phase transitions in intermediate energy heavy ion collisions, supported by theoretical modeling.

## Contribution

It introduces the multiplicity derivative as a new observable for detecting first order phase transitions in heavy ion collisions.

## Key findings

- Derivative of M peaks at transition energy
- Maximizes where specific heat Cv peaks
- Feasible measurement in multiple labs

## Abstract

Measurement of M, the total multiplicity, for central collision between comparable mass heavy ions can provide a signature for first order phase transition. The derivative of M with respect to E*/A where E* is the excitation energy in the centre of mass and A the total mass of the dissociating system is expected to go through maximum as a function of E*. Theoretical modelling shows that this is the energy where the specific heat Cv maximizes which typically happens at first order phase transition. The measurement of total M is probably feasible in more than one laboratory.