Approved Plots from CMS First Beam Runs 2-October-2008

First Beam Results 2 First Events: Beam going through CMS Beam Pickup (ch1) CMS Beam Condition Monitors (ch 3, 4)

First Beam Results 3 Sep 10 - first multiple orbits BPTX orbit signals

First Beam Results 4 Pictures from Sept.10 – First Beams through CMS Point 5 Control Room CMS Centre Meyrin

First Beam Results 5

6 Different projections of a splash event HCAL energy ECAL energy DT muon chamber hits debris Inner tracking systems kept OFF ~2x10 9 protons on collimator ~150 m upstream of CMS

First Beam Results 7 ECAL beam splash event from Sept. 10, White areas in ECAL barrel are trigger towers masked from the readout. The ECAL endcaps are uncalibrated (lowest gain photodetectors are nearest the beam pipe) ECAL Energy from Splash Event

First Beam Results 8 CMS 146 m TAN TCTV TCTH MBRC TCLP Correlation between the total energy deposit in ECAL and in the beam loss monitoring detectors. The diagram shows the location of the beam loss monitors next to the collimators.

First Beam Results 9 Uncorrected HCAL Energy from Collimator Event Distribution of equivalent energy across the CMS Hadron Calorimeters in a beam-on-collimator event during September This plot has been not been adjusted for cross-sectional area effects, which produce the structures seen at |  | = 2.8.

First Beam Results 10 Corrected HCAL Energy from Collimator Event Distribution of equivalent energy across the CMS Hadron Calorimeters in a beam-on-collimator event during September In this plot, the reported energy has been corrected for the cross-sectional area of each tower in the endcap and for the length of scintillator in the barrel.

First Beam Results 11 Correlation of ECAL and HCAL Barrel Correlation between reconstructed energy in the CMS Hadron Barrel Calorimeter (HB) and Electron Barrel Calorimeter (EB) for beam-on- collimator events in September The large reconstructed energy values are the result of the hundreds of thousands of muons which passed through the detector during each event.

First Beam Results 12 Synchronization of HCAL from Splash Events

First Beam Results 13 HCAL Splash Delays Before Tuning This plot shows the difference between predicted pulse arrival time and mean pulse arrival time for the beam-on-collimator events of September 10, The HCAL barrel uses tuned integration delays in this data, while the other sections of the detector are not tuned. This result combines events from both LHC beams, which cancels several systematic effects.

First Beam Results 14 HCAL Splash Delays After Tuning This plot shows the difference between predicted pulse arrival time and mean pulse arrival time for the beam-on-collimator events of September 18, This data set uses delays tuned from the previous beam-on-collimator runs, except for a small region of the outer hadron calorimeter which has since been corrected. This result uses events from only a single beam of LHC and some residual systematic effects are present.

First Beam Results 15 HCAL Splash Delays After Tuning and HO partly removed This plot shows the difference between predicted pulse arrival time and mean pulse arrival time for the beam-on-collimator events of September 18, This data set uses delays tuned from the previous beam-on-collimator runs, except for a small region of the outer hadron calorimeter which has been omitted in this plot. This result uses events from only a single beam of LHC and some residual systematic effects are present.

First Beam Results 16 HCAL Endcap Energy Before/After Capture These figures show the distribution of energy observed in the CMS Endcap Hadron Calorimeter before and after capture of the LHC by the RF system. Before beam capture the high rate of energy deposit near the beamline is quite clear, while the beam after capture is quite clean.

First Beam Results 17 Evidence for Beam Gas Collisions in HF Energy Average energy as a function of eta in the CMS Forward Hadron Calorimeter (HF) for circulating beam events at LHC. The events in question are triggered by the HF from LHC's Beam 2, which passes through the CMS Detector from negative to positive z. The events further selected to contain at least one deposit of 20 GeV in a tower which is registered by both the long and short fiber sections of the tower. These sections measure the total energy and the hadronic energy of a shower, respectively. The peak in energy deposition towards positive pseudorapidity is a signature of beam-gas interactions near or within the detector, as the remnants of beam-gas interactions will have a small transverse momentum and a larger longitudinal momentum from the initiating proton.

First Beam Results 18 Muon chambers or calorimeter? Linearity of the number of hits in the third ring of DT chambers vs. total ECAL energy for splash events

First Beam Results 19 Beam Halo Muons Reconstructed in CSCs Three muons are reconstructed in the Cathode Strip Chambers (CSC's). The chambers with hits are shown as trapezoidal volumes in white, with yellow strips running in the radial direction, and purple wires running in the azimuthal direction. The long blue lines threading several chambers represent muon trajectories reconstructed offline. One line appears to be bent due to multiple scattering of the muon in the calorimeter. This particular beam halo / beam gas event is unusual in having three reconstructed muons; most events have one.

First Beam Results 20 CSC Halo Muons Single and double halo muon events

First Beam Results 21 CSC and DT Halo Muon Event

First Beam Results 22 CSC – HCAL halo muon Halo muon observed traversing between both CSC endcaps and leaving a pattern of energy in the barrel hadron calorimeter X-Y projection on next page

First Beam Results 23 CSC – HCAL Halo Muon This is an XY view of the hadronic calorimeter showing a large measured energy due to a beam muon which was tracked in the CSC's. The muon is coming out of the page. The strips (green) and wires (purple) which register the incoming muon are also displayed. The muon is coming in at an angle, so the intersection point of the strips and wires does not line up with the tower, which has 7.6 GeV.

First Beam Results 24 CSC – HCAL Halo Muon Halo muon observed traversing between both CSC endcaps and leaving a pattern of energy in the barrel hadron calorimeter X-Y projection on next page

First Beam Results 25 CSC – HCAL Halo Muon This is an XY view of the hadronic calorimeter showing a large measured energy due to a beam muon which was tracked in the CSC's. The muon is coming out of the page. The CSC strips (green) and wires (purple) which register the incoming muon are also displayed. In this event, the intersection point of the strips and wires line up nicely with the calorimeter tower, which has an energy of 4.3 GeV.

First Beam Results 26 Halo and Cosmic Muon Angles This plot shows the distribution of the angles of reconstructed muon tracks with respect to the plane perpendicular to the beam. One expects beam halo muons to make a small angle, and this is illustrated by the blue histogram. In contrast, muons from cosmic rays should pass through the cathode strip chambers at a more oblique angle, and this is what we see when the beam is off (black histogram). When the beam is on (orange-shaded histogram) the distribution consists of two pieces, one of which closely resembles cosmic rays, and the other which matches the beam halo simulation. The normalization of the blue and black histograms are not based on any calculation; they are meant to guide the eye.

First Beam Results 27 Beam Halo Hit Distribution ME  4ME  3ME  2ME  1 ME+1ME+2ME+3ME+4 Arrow indicates order beam traversed endcap disks

First Beam Results 28 Online CSC Halo Muon Rates during LHC Beam Capture This plot shows the CSC halo trigger rate in the MINUS endcap as a function of time. The yellowish band indicates the first successful RF capture of the LHC beam (beam 2) which lasted about 10min (and ended with the first automatic beam abort). One sees rate jumps preceding this due to earlier capture attempts. These rates are defined by averaging over a 10 s interval. Sectors 1 and 6 are mostly horizontal on the inside part of the ring