Tests of a Roman Pot Prototype for the TOTEM Experiment

3 pages, 8 figures, proceedings of PAC05, Knoxville, Tennessee, USA, May 2005The TOTEM collaboration has developed and tested the first prototype of its Roman Pots to be operated in the LHC. TOTEM Roman Pots contain stacks of 10 silicon detectors with strips oriented in two orthogonal directions. To measure proton scattering angles of a few microradians, the detectors will approach the beam centre to a distance of 10 sigma + 0.5 mm (= 1.3 mm). Dead space near the detector edge is minimised by using two novel "edgeless" detector technologies. The silicon detectors are used both for precise track reconstruction and for triggering. The first full-sized prototypes of both detector technologies as well as their read-out electronics have been developed, built and operated. The tests took place first in a fixed-target muon beam at CERN's SPS, and then in the proton beam-line of the SPS accelerator ring. We present the test beam results demonstrating the successful functionality of the system despite slight technical shortcomings to be improved in the near future.Peer reviewe

TOTEM Physics

This article discusses the physics programme of the TOTEM experiment at the LHC. A new special beam optics with beta* = 90 m, enabling the measurements of the total cross-section, elastic pp scattering and diffractive phenomena already at early LHC runs, is explained. For this and the various other TOTEM running scenarios, the acceptances of the leading proton detectors and of the forward tracking stations for some physics processes are described.Peer reviewe

GEM-TPC Trackers for the Super-FRS at FAIR

For the slow extraction part of the beam diagnostics system of the Superconducting Projectile Fragment Separator (Super-FRS) of FAIR-facility a total of 32 detectors are needed. They will be used for beam monitoring, tracking and characterization of the produced ions. GEM-TPC detectors can perform over wide dynamic range without disturbing the beam and are thus suitable for this kind of in-beam detection. We present the simulations and first measurements with the GEMs of the Super-FRS GEM-TPC prototype

TOTEM early measurements

The status of the TOTEM experiment is described as well as the prospects for the measurements in the early LHC runs. The primary goal of TOTEM is the measurement of the total p-p cross section, using a method independent of the luminosity. A final accuracy of 1% is ex- pected with dedicated β∗ = 1540 m runs, while at the beginning a 5% resolution is achievable with a β∗ = 90 m optics. Accordingly to the running scenarios TOTEM will be able to measure the elastic scattering in a wide range of t and to study the cross-sections and the topologies of diffractive events. In a later stage, physics studies will be extended to low-x and forward physics collaborating with CMS as a whole experimental apparatus.Peer reviewe

Physics and Beam Monitoring with Forward Shower Counters (FSC) in CMS

We propose to add forward shower counters, FSC, to CMS along the beam pipes, with 59 m $\lesssim z \lesssim$ 140 m. These will detect showers from very forward particles with $7 \lesssim \eta \lesssim 11$ interacting in the beam pipe and surrounding material. They increase the total rapidity coverage of CMS to nearly $\Delta\Omega = 4\pi$, thus detecting most of the inelastic cross section $\sigma_{inel}$, including low mass diffraction. They will help increase our understanding of all high cross section processes, which is important for understanding the ``underlying event'' backgrounds to most physics searches. To the extent that the luminosity is well known, they may (together with all of CMS) provide the best measurement of $\sigma_{inel}$ at the LHC. They are most useful when the luminosity per bunch crossing is still low enough to provide single (no pile-up) collisions. They will allow measurements of single diffraction: $p+p\rightarrow p \oplus X$ (where $\oplus$ means a rapidity gap) for lower masses than otherwise possible, and double diffraction: $p + p \rightarrow X \oplus X$ with a large central rapidity gap. They can also be used as rapidity gap detectors for double pomeron exchange and central exclusive processes. Studies of exclusive processes such as $\gamma\gamma \rightarrow \mu^+\mu^-$ (for luminosity calibration and eventually momentum calibration of forward spectrometers) can be made more cleanly requiring gaps in the FSC counters. Models of forward particle production can be tested indirectly through simulations of hit patterns in the counters. This may reduce the uncertainty on very high energy ($E \sim 10^{17}$ eV) cosmic ray shower parameters. For heavy ion collisions, the counters act as crude forward calorimeters detecting nuclear fragments (supplementing the ZDC), as well as enabling the study of coherent quasi-elastic scattering e.g. Pb + Pb $\rightarrow$ Pb $\oplus X \oplus$ Pb via two-photon interactions. The counters can also be used for real-time monitoring, and if desired for vetoing in the level 1 trigger,both incoming and outgoing beam halo-generated backgrounds (separated by timing) and beam conditions generally. These counters represent a significant enhancement of the beam monitoring, and will make an invaluable contribution to the understanding of the background environment and its topology. They can also provide an additional luminosity monitor, up to luminosities such that the number of interactions per bunch crossing is $\langle n_X \rangle \sim 5$. This note discusses mainly the physics issues; more technical details will be presented in another note. Basically we propose a set of scintillation counters at several locations between 59 m and 140 m along the beam pipes (on both sides), and read out by DAQ electronics identical to that of the HF, with some inputs to the level 1 trigger. Bunch-by-bunch information on rates etc. will be provided for LHC operations. The cost is very modest, given the added value to many physics studies in CMS and to our knowledge of beam conditions generally