LISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
A Very Forward ProtonA Very Forward ProtonSpectrometer for H1Spectrometer for H1
Pierre Van MechelenPierre Van Mechelen
Universiteit Antwerpen (UIA)Universiteit Antwerpen (UIA)
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Participating GroupsParticipating Groups
University of Antwerp (UIA), BelgiumUniversity of Antwerp (UIA), BelgiumT. Anthonis, E. A. De Wolf, P. Van MechelenT. Anthonis, E. A. De Wolf, P. Van Mechelen
Inter-University Institute for High Energies (ULB-Inter-University Institute for High Energies (ULB-VUB), VUB),
Brussels, BelgiumBrussels, BelgiumL. Favart, X. Janssen, D. Johnson, P. Marage, R. RoosenL. Favart, X. Janssen, D. Johnson, P. Marage, R. Roosen
University of Hamburg II, GermanyUniversity of Hamburg II, GermanyV. Blobel, F. Büsser, V. Jemanov, A. Meyer, B. Naroska,V. Blobel, F. Büsser, V. Jemanov, A. Meyer, B. Naroska,
F. Niebergall, J. Schütt, H. Spitzer, R. van StaaF. Niebergall, J. Schütt, H. Spitzer, R. van Staa
University of Lund, SwedenUniversity of Lund, SwedenL. Jönsson, H. Jung, U. MjörnmarkL. Jönsson, H. Jung, U. Mjörnmark
University of Birmingham, UKUniversity of Birmingham, UKP. NewmanP. Newman
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Diffraction Physics at HERADiffraction Physics at HERA
• HERA I (1992-2000): HERA I (1992-2000):
– large fraction (~10%) of “large rapidity gap” eventslarge fraction (~10%) of “large rapidity gap” events
– strong theoretical interest (understanding in QCD)strong theoretical interest (understanding in QCD)
– measurements of measurements of FF22DD, incl. final states, jets, charm, excl. VM, incl. final states, jets, charm, excl. VM
– results: soft/hard transition, gluon dominance, DGLAP results: soft/hard transition, gluon dominance, DGLAP consistencyconsistency
– limitations: rapidity gap selection yields large systematic errors, limitations: rapidity gap selection yields large systematic errors, low statistics, limited low statistics, limited t t and and measurement measurement
• HERA II (2001-2006):HERA II (2001-2006):
– major upgrade of the H1 detectormajor upgrade of the H1 detector
– high luminosity regime high luminosity regime need for efficient VFPS-trigger need for efficient VFPS-trigger
– need for clean selection by tagging the scattered protonneed for clean selection by tagging the scattered proton
– need for measurement of proton momentum (need for measurement of proton momentum (xxIPIP ,, t t, , ))
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
The H1 Forward Proton The H1 Forward Proton SpectrometerSpectrometer• Horizontal stations:Horizontal stations:
– at 60 m and 80 m from I.P.at 60 m and 80 m from I.P.
– acceptance of a few % at acceptance of a few % at high |high |t t | and low | and low xxIPIP
• Vertical stations:Vertical stations:
– at 81 m and 90 m from I.P.at 81 m and 90 m from I.P.
– large acceptance at low |large acceptance at low |tt | and large | and large xxIPIP
• Measurement of Measurement of FF22LPLP::
year lumi events FPS-V 1995 1.4 pb-1 1661 FPS-H 1999/2000 28.8 pb-1 3100
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
VFPS LocationVFPS Location
• VFPS location is optimised for VFPS location is optimised for acceptance acceptance 220m NL 220m NL
• Proton beam is approached Proton beam is approached horizontally (use HERA bend)horizontally (use HERA bend)
• Bypass is needed to re-route Bypass is needed to re-route the cold beam linethe cold beam line
xxIPIP = 0.01 = 0.01
H1
ZEUS
VFPS
HERMES
HERA-B
present FPS VFPS
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Bypass of Cold Beam LineBypass of Cold Beam Line• Cold section HPNL-220:Cold section HPNL-220:
– modification of 10 m drift segment with easy accessmodification of 10 m drift segment with easy access
– p p -beam above -beam above e e -beam-beam
– horizontal bypass for helium and superconductor lineshorizontal bypass for helium and superconductor lines
– new (warm) beam pipenew (warm) beam pipe
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
VFPS DetectorsVFPS Detectors
• VFPS detectors similar to FPS:VFPS detectors similar to FPS:
– 2 “Roman Pot” stations equipped 2 “Roman Pot” stations equipped with with 2 scintillating fibre detectors each2 scintillating fibre detectors each
– 1 fibre detector measures both 1 fibre detector measures both u u - - and and v v - co-ordinates- co-ordinates
• 5 fibres/light guide 5 fibres/light guide 8.2 photo- 8.2 photo-electrons electrons 99.4% detection 99.4% detection efficiencyefficiency
• Staggered fibres properties:Staggered fibres properties:diameter 480 µm pitch 340 µm cladding 30 µm theoretical resolution 63 µm prototype test resolution 94 µm
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Triggering Diffractive DIS at Triggering Diffractive DIS at HERA-IIHERA-II• HERA-I strategy:HERA-I strategy:
– inclusive trigger based on inclusive trigger based on backward calorimeter (SPACAL) backward calorimeter (SPACAL) and vertex requirement and vertex requirement (MWPC)(MWPC)
– off-line rapidity gap selection off-line rapidity gap selection
• HERA-II: HERA-II:
– factor 5 increase in luminosityfactor 5 increase in luminosity
– factor 2 increase in beam factor 2 increase in beam currents currents
– inclusive triggers are pre-scaledinclusive triggers are pre-scaled
• Rapidity gap trigger unfeasibleRapidity gap trigger unfeasible
• Level-1 VFPS trigger neededLevel-1 VFPS trigger needed
HERA-I 100 Hz HERA-I < 174° 30 Hz HERA-II < 174° 175 Hz
FPS HERA-I 10 kHz FPS HERA-II 20 kHz VFPS HERA-II 60 kHz
SPACAL/MWPC trigger rates:
(V)FPS trigger rates:
coincidence rates:
background 1.0 Hz physics 0.4 Hz total 1.4 Hz
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
• Linear beam transport:Linear beam transport:
• Non-linear corrections:Non-linear corrections:
– non-linear effects in energy deviation non-linear effects in energy deviation xxIPIP
– sextupolessextupoles
– offset, tilted magnetsoffset, tilted magnets
Simulation StudiesSimulation Studies
IP
xxxx
xxx
x
x
x
DTT
DTT
x
x
0
100 0
0
02221
1211
diffractiveep scattering
beam spreadand divergence at
I.P.
position, slope and
energy at VFPS
beam optictransport matrix
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
AcceptanceAcceptance
• Simulation includes detailed Simulation includes detailed description of beam pipedescription of beam pipe
• HERA machine crew agreed to HERA machine crew agreed to steer proton beam away from steer proton beam away from critical acceptance losscritical acceptance loss
• Detectors approach beam up to Detectors approach beam up to “12-sigma” from inside HERA “12-sigma” from inside HERA ring ring + 3 mm “coasting beam + 3 mm “coasting beam margin”margin”
• Acceptance range:Acceptance range: FPS-H FPS-V VFPS |t |- range 0.2 0.4 0 0.15 0 0.25 xIP - range 10-5 10-2 0.05 0.15 0.01 0.02 local acc. < 30% ~ 100% ~ 100%
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
ReconstructionReconstruction
• Reconstruction fit:Reconstruction fit:
where where ccijij is a covariance matrix containing: is a covariance matrix containing:
– beam covariancebeam covariance
– fibre detector resolutionfibre detector resolution
jiyxIPjjijyxIPii xxxcxxx
,
12 ,,,,
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
ResolutionResolution
• Resolution is dominated by beam covariance (but still Resolution is dominated by beam covariance (but still sensitive to fibre detector resolution)sensitive to fibre detector resolution)
• xxIPIP resolution is competitive with reconstruction of resolution is competitive with reconstruction of xxIPIP by H1 by H1
• ~ 4 bins in |~ 4 bins in |t t ||
• ~ 15 bins in ~ 15 bins in for | for |tt | > 0.2 GeV | > 0.2 GeV22
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
• Relative positioning of Relative positioning of detectors versus nominal detectors versus nominal proton beamproton beam
• Exploit kinematic peak and Exploit kinematic peak and xxIP IP -measurement by H1-measurement by H1
• Calibration fit:Calibration fit:
• Alignment precision of ~100 Alignment precision of ~100 m is feasiblem is feasible
• Alternative fits are possible Alternative fits are possible with e.g. elastic with e.g. elastic mesonsmesons
AlignmentAlignment
2
21
2
2
2
22
1HIPIPyx xx
HIPIPyx xx
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Expected ResultsExpected Results
• Inclusive diffraction:Inclusive diffraction:
– luminosity: 350 pbluminosity: 350 pb-1-1 (3 years of (3 years of HERA-II running, 50% VFPS HERA-II running, 50% VFPS operation efficiency)operation efficiency)
– test of hard scattering fact.:test of hard scattering fact.:FF22
D D ((, Q, Q 22) at fixed ) at fixed xxIPIP , |, |t t ||
– uncorrelated systematic errors uncorrelated systematic errors can approach the level of can approach the level of FF22 (few (few %)%)
– event yields:event yields:
event sample no coasting beam coasting beam acceptance > 80% 1,100,000 390,000 0 < |t| < 0.2 GeV2 1,800,000 810,000 0.2 < |t| < 0.4 GeV2 330,000 160,000 0.4 < |t| < 0.6 GeV2 47,000 23,000 0.6 < |t| < 0.8 GeV2 6,000 3,000
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Expected ResultsExpected Results
• Hadronic final states:Hadronic final states:
– Open charm production:Open charm production:• 1996/97 1996/97 D*D* analysis yielded 46 analysis yielded 4610 10
ev.ev.
• full HERA-I data sample: factor 2-3full HERA-I data sample: factor 2-3
• HERA-II/VFPS expectation: 380 ev.HERA-II/VFPS expectation: 380 ev.
– Diffractive dijet electroproduction:Diffractive dijet electroproduction:• 1996/97 dijet analysis yielded 2500 1996/97 dijet analysis yielded 2500
ev.ev.
• HERA-II/VFPS expectation: 22900 HERA-II/VFPS expectation: 22900 ev.ev.
– Diffractive dijet photoproduction:Diffractive dijet photoproduction:• HERA-II/VFPS expectation: HERA-II/VFPS expectation:
• eTag-6 (eTag-6 (WW = 275 GeV): 1400 ev. = 275 GeV): 1400 ev.
• eTag-40 (eTag-40 (WW = 140 GeV): 20000 ev. = 140 GeV): 20000 ev.
open charm production
dijet electroproduction
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
Expected ResultsExpected Results
• Azimuthal asymmetryAzimuthal asymmetry
– angle between proton and electron scattering planes (angle between proton and electron scattering planes () ) gives a handle on gives a handle on T T and and LL and their interference terms: and their interference terms:
– 15 bins with each 10,000 events!15 bins with each 10,000 events!
– study asymmetry as a function of study asymmetry as a function of , , QQ 22
• Deeply Virtual Compton ScatteringDeeply Virtual Compton Scattering
– only 25 DVCS observed in 1997only 25 DVCS observed in 1997
– HERA-II/VFPS expectation: 3600 events (HERA-II/VFPS expectation: 3600 events (QQ 22 > 8 GeV > 8 GeV22))
– VFPS adds to H1-triggered DVCS, mostly at low VFPS adds to H1-triggered DVCS, mostly at low WW, low , low QQ 22
2coscos12 TTLTLT
D
dd
Pierre Van MechelenLISHEP 2002 – Rio de Janeiro, Brazil – February 4-8, 2002
TimelineTimeline
ConclusionConclusion
• VFPS mandatory to trigger diffraction at HERA-IIVFPS mandatory to trigger diffraction at HERA-II
• Very good acceptance in narrow window around Very good acceptance in narrow window around xxIPIP = 0.01 = 0.01
• Good resolution on reconstructed proton momentum will Good resolution on reconstructed proton momentum will allow exciting physics analysesallow exciting physics analyses
• DESY-PRC approved the project in October 2001DESY-PRC approved the project in October 2001
• Bypass and VFPS construction are on scheduleBypass and VFPS construction are on schedule
• Insertion in HERA machine is foreseen for early 2003 Insertion in HERA machine is foreseen for early 2003 shutdownshutdown
• Data taking from 2004 to 2006...Data taking from 2004 to 2006...
