1. The Design of a Detector for the Electron Relativistic Heavy Ion Collider Anders Ingo Kirleis 1, William Foreman 1, Elke-Caroline Aschenauer 2, and Matthew Lamont 2 1 SUNY at Stony Brook, Stony Brook NY 11790 & 2 Physics Department, Brookhaven National Laboratory, Upton, NY 11973 August 2009 The proposed construction of the Electron Relativistic Heavy Ion Collider (eRHIC) at Brookhaven National Laboratory (BNL) will begin a new experimental quest to study the gluons that bind all matter. The main goal is to design a detector for eRHIC that is able to cover a large acceptance and separate the different particle types expected to be seen. To do this, it was first necessary to perform computerized simulations using Monte Carlo event generators which allow scientists to model the interactions during a collision to reveal the inner structure of the hadrons. Software programs such as PYTHIA and ROOT were used to determine the properties of the events and the individual particles. After analysis of this data, we were able to construct a three- dimensional image of a preliminary detector design using GEANT software. Preliminary calculations have determined that our solenoid’s length will be 5 m and have a magnetic field strength of 4 T. We will have also have forward and rear dipole magnets each 3 m long of 1 T in the forward and rear sections. This setup, together with a silicon vertex tracker around the IP and other tracking chambers, will guarantee that the particle momenta can be measured with high accuracy. To detect neutral particles, an electromagnetic calorimeter also needs to be included. It will have five sections: forward, forward cap, barrel, rear cap, and rear made out of lead glass. The hadronic calorimeter will have three sections: barrel, rear cap, and rear. It will be constructed from lead and scintillator. A high threshold Cerenkov will be present in the forward cap to allow fast triggering on the scattered lepton. A ring imaging Cerenkov counter (RICH) will be present in the rear cap. It will have two radiators one composed of 5 cm Aerogel and the other of C 4 F 10. The RICH together with a detector of internally reflected Cerenkov light in the barrel section will enable us to separate pions, kaons, and protons. These preliminary designs are an excellent starting point for the future development of the eRHIC detector. We are working closely with the collider-accelerator department as the size of the interaction regions places constraints on the size of the detector. Calorimetry A calorimeter in particle physics is a device which measures the energy of particles. When particles enter the calorimeter, a particle shower occurs at which time the energy is collected and analyzed. An electromagnetic calorimeter is one specifically designed to measure the energy of particles that interact via the electromagnetic interaction, i.e.   , while a hadronic calorimeter is one designed to measure particles that interact via the strong nuclear force. Below we see the preliminary calorimeter design by itself. The electromagnetic calorimeter can be seen in blue and the hadronic calorimeter in green. Magnets Our design calls for a solenoid and two dipole magnets. The solenoid consists of wire coils wrapped around an iron core which, when an electric current passes through, produces an electric field of strength 4 T. Its main purpose is to bend the particles in the detector. Their momentum is determined from their curvature. The solenoid is shown below in red in the barrel. The dipole magnet creates a homogeneous magnetic field over some distance. It's purpose is to twofold: on one hand it is integrated in the accelerator to bend the particles so they collide in the detector and it is needed to detect low momentum particles from the collision. The dipole magnets are seen below in violet in the forward and rear regions. Particle Identification Our design has a Detector of Internally Reflected Cerenkov light (DIRC), a High Threshold Cerenkov Counter(HTCC), and a Ring Imaging Cerenkov Counter (RICH). A DIRC can separate pions, kaons and protons up to 4 GeV with high efficiency. It can be seen below in blue in the barrel region. The main function of the HTCC is to aid in the identification of electrons. It uses CO 2 as a radiator providing a high threshold such that will cause electrons to emit Cerenkov light. The HTCC can be seen below in red in the forward region. The RICH is filled with C 4 F 10 gas combined with aerogel which will help to separate pions, kaons, and protons from each other. It can be seen below in green in the rear region. Tracking Results: Full Design Below we see all components together in the first ever electron relativistic heavy ion collider design using GEANT. Abstract Preliminary Design Proposed Location Outlook From this point, steps can be taken to further develop the design of the detector. Magnetic fields and materials must be defined in the GEANT language where, once implemented, will allow scientists to more realistically simulate, what is happening during a collision using PYTHIA visually along with the three dimensional design view. GEANT simulates the detector response, a crucial element in allowing for excellent further analysis. Acknowledgements Matthew Lamont Elke-Caroline Aschenauer Abhay Deshpande Pavel Nevski Thomas Ullrich The EIC Task Force Melvyn Morris and the OEP Staff Steven Vigdor Samuel Aronson We will have several tracking detectors which will allow us to determine the momentum and position of the outgoing hadrons and leptons. These tracking devices can be seen below outlined in black. The Central vertex tracking detector can be seen in the barrel region as it is encased in a yellow tube. It consists of a jet type drift chamber. Particle tracking at small forward and backward angles to the beam is done with planar drift chambers. The decays of short lived particles can be detected in a vertex detector which has a time-expansion type drift cell structure. For reference purposes the interaction point can be seen as a red star in the barrel region. Background Photo: Google Earth