First data from TOTEM
experiment at LHC
Fabrizio Ferro - INFN Genova
Diffraction 2010
Fabrizio Ferro – INFN Genova
TOTEM phyics
Total cross-section
Elastic Scattering
b
Forward physics (with CMS)
Diffraction: soft and hard (with CMS)
Diffraction 2010
Fabrizio Ferro – INFN Genova
Total pp cross section
Current models predict for
14 TeV: 90 – 130 mb
Aim of TOTEM: ~ 1%
“First year”
: ~5%
COMPETE
Collaboration:
special optics
Luminosity independent method:
Diffraction 2010
Fabrizio Ferro – INFN Genova
Physics with high b* optics
log(|t|)/Gev2
-t = 4·10-4
0.012
0.3
2.5
Total cross section measurement at ~5 % (~1%)
Elastic scattering: 0.0004<|t|< 2.5 GeV2
Soft diffraction: all masses - 65 % of diffractive protons seen
Classification of inelastic events: rates & multiplicity
Diffraction 2010
Fabrizio Ferro – INFN Genova
Physics with low b*
Hits in RP220
Single diffraction
ds/dM : 0.025<x<0.15
1 < M < 3 TeV
s(M)/M ~ 2 - 5%
Acceptance
Hits in RP220
Central diffraction
ds/dM : 200 < M < 1000 GeV
s(M)/M ~ 2 - 5%
Log M(GeV)
Elastic scattering
0.5< |t| < 5 GeV2
s(|t|) ~ 0.2√ |t|
Diffraction 2010
Fabrizio Ferro – INFN Genova
TOTEM detectors
Telescopes:
10.5 m
TAS
14 m
Roman Pot stations in the
LHC tunnel
Diffraction 2010
RP (147 m)
Fabrizio Ferro – INFN Genova
RP (220m)
T1 telescope (1)
2 arms of CSCs for track and vertex
reconstruction
3.1<|h|<4.7 - Df=2p
• Both T1 arms on the test
line. Ready for installation.
Diffraction 2010
Fabrizio Ferro – INFN Genova
T1 telescope (2)
efficiency
Both arms successfully tested with pion and muon beams
Pions on copper target to get many-tracks events
p reconstructed hits
CSC efficiencies with muons
(triple coincidences)
Longitudinal vertex
Cu
Transverse vertex
target
Beam
monitor
frame
Diffraction 2010
Fabrizio Ferro – INFN Genova
T2 telescope
2 arms of GEMs for tracks and vertex reconstruction
3.1<|h|<4.7 - Df=2p
Both arms installed and
taking data
Diffraction 2010
Fabrizio Ferro – INFN Genova
T2 event at 7 TeV
Diffraction 2010
Fabrizio Ferro – INFN Genova
Alignment and vertex reconstruction
Before
RMS=1.4cm
RMS=1.7cm
RMS=3.1m
After
RMS=0.8cm
Diffraction 2010
RMS=1.0cm
Fabrizio Ferro – INFN Genova
RMS=2.3m
h distribution
Tracks pointing to
vertex
Statistical
error only
BeamPipe cone at h~5.53
Diffraction 2010
Fabrizio Ferro – INFN Genova
TOTEM Roman Pots
Diffraction 2010
Fabrizio Ferro – INFN Genova
Roman pot alignment
Critical and fundamental for any physics measurement
To align proton detectors means:
Resolve misalignments within detector assembly → methods: local track
Resolve relative positions of the pot:
principal information source: motor control (→ calibration, reliability, …)
→ method: local track based (detector overlap)
Resolve position of beam (uncertainties and variations of optics):
→ method: profiles from physics events, Beam Halo
Cross-check: Beam Position Monitors ; Alignment with collimators
Resolve left-right position
→ method: global (elastic) track based
Diffraction 2010
Fabrizio Ferro – INFN Genova
Roman Pot alignment (at 20s)
Vertical alignment
sectors 5-6 (IP5 minus side)
Tracks in horizontal pot
preliminary
Diffraction 2010
sectors 4-5 (IP5 plus side)
Tracks in horizontal pot
preliminary
Fabrizio Ferro – INFN Genova
Roman Pot alignment (at 20s)
Horizontal alignment
sectors 4-5 (IP5 plus side)
preliminary
Diffraction 2010
Halo protons
Tracks in horizontal pot
Tracks in vertical pot
sectors 5-6 (IP5 minus side)
preliminary
Fabrizio Ferro – INFN Genova
“Diffractive” protons at 7 TeV
preliminary
TOP
Raw distributions, no
selection:
Diffractive protons +
background
preliminary
BOTTOM
Estimated Dp/p : 0.06 - 0.12
Diffraction 2010
Fabrizio Ferro – INFN Genova
A first elastic scattering candidate
RPs at 25s
Run 1964.004
Event 13682
Diffraction 2010
Fabrizio Ferro – INFN Genova
Analysis and data taking still in progress
Data taking with RP at 25s : collected ~ 3 M events with RP only
~5M
“
RP + T2
Data taking with RP at 20s : collected ~ 6 M RP + T2
Data taking with RP at 15s : under investigation with the machine
Full set of systematics sources under investigation:
- Alignment
- Beam position
- Beam divergence
- Background from the machine (halo, beam gas,.....)
- Multiple scattering and material interaction
- Optics : uncertainty on the optical functions, crossing angle, vertex....
and in addition:
- Estimate Efficiencies (trigger, track reconstruction....)
- Luminosity
- Physics Background & Pile-up
Diffraction 2010
Fabrizio Ferro – INFN Genova
Summary
The TOTEM Detectors installed in the LHC (RP220m and T2) have
completed the commissioning and are presently taking data
Once that the 220m RPs will be inserted at their nominal position, TOTEM
can move on to its physic program at low b*:
- high mass Single & Central Diffraction
- large |t| elastic scattering (0.65 < |t| < 5 GeV2)
- forward density of charged particles
Precise measurements of elastic, diffractive and total cross sections
require high b* optics and the installation of T1 and of RP147m
- Elastic scattering in a wider |t| range
- Diffractive physics over a larger rapidity range 3.1 <|h |< 6.5
- Single and Central Diffraction at any mass
- Measurement of stot with a precision of ~ 5 % (1%)
Diffraction 2010
Fabrizio Ferro – INFN Genova