diffraction at lhc - experimental set-up risto orava university of helsinki and helsinki institute...

$: Diffraction at LHC - Experimental set-up Risto Orava University of Helsinki and Helsinki Institute of Physics 0.1 Low-x Workshop Antwerpen R.Orava 17$
Diffraction at LHC - Experimental set-up

Risto Orava

University of Helsinki andHelsinki Institute of Physics

0.1

Low-x Workshop Antwerpen R.Orava 17. September 2002

Baseline design Criteria of ATLAS & CMS aim at discoveries at high pT

• Detection of High pT Objects: Higgs, SUSY,...• Precise measurement of e, , , , and b-jets:

tracking: || < 2.5calorimetry with fine granularity: || < 2.5muon system: || < 2.7

• Measurement of jets, ETmiss:

calorimetry extension: || < 5• Precision physics (cross sections...):

energy scale: e & 0.1%, jets 1% absolute luminosity vs. parton-parton luminosity via”well known” processes such as W/Z production?

0.2

All this complements the forward physics agenda.

Low-x 2002 Risto Orava

Important part of the phase space is not covered bythe baseline designs. Much of the large energy, smalltransverse energy particles are missed.

In the forward region (| > 5) few particles with largeenergies/small transverse momenta.

Charge flow

Energy flow

0.4

How to extend baseline LHC experiments for the benefit of forward physics?

1.1

(1) Leading proton & inelastic activity

(2) Upgrade scenarios & Forward detectors:

• ATLAS + A Foward Spectrometer

• CMS + TOTEM

• Roman Pots and MicroStations

(3) Physics Performance:

• Diffractive Processes

(4) Outlook

(TOTEM is accepted to go for a TDR)


2.1

LHC low * optics (* = 0.5m, v6.3)

Beam size is small between s=200-250m.Beam dispersion (Dx) large at s>300m: horizontal deviationfrom the nominal beam position given as: x = Dx

x

s (m)

Dx (m)


LHC optics (v6.3) layout: Two studiesend up with a similar detector lay-out

2.2

Optimized detector locations: 90m, 150m, 180m, 210m, 240m, >400m?

Totem


Thin window (3 x 2 cm2)

TOTEM : Roman Pots for leading protons

Concave bottom

The detectors approach the beam vertically (step motor)Si-detectors operated at 130K (where the Lazarus effect (V.Palmieri et al.) optimizes charge collection efficiency, reduces noise and provides radiation hardness.)

Cryogenic Si-detectors located here (RD39)

2.3

8cm

SAB 3. June 2002 Risto Orava

1m

Beam sizes and effective distances at detectorlocations define the acceptance.

Location Beam size Effective distance s(m) x(mm) eff (mm)

150 0.6 7 (13) 180 0.4 5 (9) 210 0.2 3 (5) 240 0.07 1.7 (2.4) 425 0.3 4 (7)

In defining eff, we assume: 10x (20x)• Note: beam halo rates difficult to predict at 240m’s• For the RF shielding & guard ring add 1mm dead space

2.4


CMS has reserved space for the forward detectorsin T1 and T2 regions

TOTEM @ CMS


3.1

Design of the Forward Spectrometer is Challenging since one has to:

• operate close to the beam in intense radiation environment• meet the constraints due to limited amount of space available• integrate the detectors with the machine requirements (vacuum, RF,...)• adapt to changing machine conditions (injection, special runs) require movable detectors

3.2


These requirements are common to Roman pots, Velo etc. detectorsdesigned to operate within the LHC vacuum chamber.

A novel detector for measuring the leading protons - the Microstation - is designed tocomply with the LHC requirements.

• a compact and light detector system (secondary particle emission, dimensions < 20cm, weight < 2kg)

• integrated with the beam vacuum chamber (acceptance)

• geometry and materials compatible with the machine requirements (dynamic vacuum (outgassing 10-11 atm, bake-out to 180 C), RF impedance (< 0.6m/ms), em pick-up)

• m accurcay in sensor movements (alignment)

• robust and reliable to operate (access limitations)

• Si strip or pixel detector technology (heat dissipation (< 50 mW), simplicity & radiation hardness (n flux 105 kHz/cm2, 0.25m CMOS read-out chips fully functional up to 30Mrad))

4.1

©M.Ryynänen, R.O. et al.

low-x 2002 Risto Orava

Microstation - initial design4.2

Interface side

Emergency trigger

Electrical connectors - feed throughs

Cooling connectors - circular

4.3

beam

19cm

Helsinki group/M. Ryynänen, R.O. et al.

Micro-Station


Inner tube for rf fitting

Inch worm motor

Emergency actuator

Detector

Space for cables and cooling link

Space for encoder

4.4

6cm

Microstation

Helsinki group/M. Ryynänen, R.O. et al.


Leading Proton Acceptance

- High *(=1100m)

1-x

L

1-x

L

-t (GeV2) -t (GeV2)

15 10

5.1

Acceptance > 50%for all values of -t: > 0.03 (0.02)

Acceptance > 50%for all values of : -t > 0.02 GeV2

Helsinki group/L.Salmi et al.


Proton acceptances at 210 & 425m

Acceptance limitedto > 0.03

Acceptance to > 0.003

5.2

low * (* = 0.5m)

Helsinki group/ S. Tapprogge, K.Österberg et al.

- for 20 downgrade by a factor of two


Detector

Support

PitchAdapter

APV25

Hybrid

CoolingPipe

Spacer

A Silicon Detector Module/Totem6.1

n n

p

p

Back plane extented to side using p-diffusiondepletion region up to p and no guard ring is requiredsignal picked by n-strip up to p-diffusion<10m dead space at the edge of the detector

p back plane

p diffusion

n strip

Detecting Higgs Boson in pp p+X+p

P

P

p1

p2

p1’

p2’

H

MH2 = 1 2 s

In symmetric case (1 = 2 = ) for MH = 140 GeV: = 0.01 ( = 40%)

(pp p+H+p) 3 fb at s = 14TeV

M/M 1%

7.1

Helsinki group/J.Lamsa, R.O.


DPE Mass Measurement at 400m

Mass resolution vs. central massassuming xF/xF = 10-4

symmetric case:

Central Mass (GeV)

Mass r

esolu

tion

(G

eV

)

M = (1.0 - 3.0) GeV (xF/xF = (1-2)10-4)

65% of the data

20 GeV < MX < 160 GeV

(MXmax determined by the aperture of the last dipole,B11, MXmin by the minimum deflection = 4mm)

7.6



- Physics Performance Figures

8.1

Inelastic activity can be extended to cover (low *)• Charged particles within 3(5.7) < ||< 7(8.4) • Luminosity monitoring for 5.2 < ||< 6.6

Leading protons can be detected (low *, >50% efficiency):• > 410-2 (180m), > 2.010-2 (210m), > 10-2 (240m), > 2.010-3 (300m, 425m) (10x approach, for 20x, factor 2 downgrade)

Missing mass:• For 20 GeV < MX < 160 GeV achieve 1% mass resolution

Dedicated runs with * = 1100m (3500m??):• Measure elastic protons down to -t = 410-3 GeV2 (240m assumed)• Measure diffractive protons down to > 0.03 (180m)


A typical pile-up event

A candidate with ET > 50 GeV1) LVL 1 trigger2) Pair of protons3) Pair of jets4) Kinematic fit5) 3D vx

(1) At LVL 1 Trigger (< 2.5): Use the minimum combined transverse energy of two central jets ET1 + ET2 > 100 GeV and the difference between the azimuthal angles of the two jets: 1 - 2= 180o (within a given cell size of x = 0.5 x 20o) to suppress the background event rate. A relative suppression of 104 (3 kHz LVL 1 trigger rate at L = 1034) achieved.

(2) At a later stage of data collection: Use the measured pair of forward-backward protons to calculate the missing mass: Mmissing

2 = (pi1+pi2-pf1-pf2)2 . Match this with the direct jet-jet effective mass.

(3) Investigate the central pair of jets to measure and identify the decay products in a model independent way.

Event Selection Strategy5.7



A model independent analysis of new centrallyproduced particle states.

Table 2. Tagging efficiencies Tagging condition Central Diffractive Non-Diffractive

0.2x10o 0.5x20o 0.2x10o 0.5x20o

Condition (1) 0.15 0.21 1.6x10-4 2.8x10-4

Condition (2) 0.12 0.16 2.5x10-5 1.2x10-4

Condition (3) 0.14 0.21 2.0x10-5 8.5x10-5

Condition (4) 0.12 0.16 1.0x10-5 4.0x10-5

Tagging Large ET Jet Pairs

Minimum combined transverse energy of two central jets (< 2.5), ET1 + ET2 = 100 GeV(2) Condition (1) and the difference between the azimuthal angles of the two jets: 1 - 2= 180o (within a given cell size of x = 0.2 x 10o and 0.5 x 20o)(3) Condition (1) and ET1 – ET2 < 10 GeV(4) Condition (1) and Condition (2) and Condition (3)

As a conclusion: a rejection factor between 103 to 104 can be obtained by applying the transverse energy based selection on a central pair of jets depending on whether an additional selection on the angular difference between the jet axes is applied or not.

10


Requiring two jets (anywhere within ||<3.2) in the detector, each above the ET threshold given below (size of 0.8*0.8 in ), the following rates can be expected for 1033:

ET > LVL1 rate 20 GeV 40 kHz

40 GeV 6 kHz

60 GeV 2 kHz

80 GeV 0.7 kHz

100 GeV 0.3 kHz

i.e. with a rejection factor of 103 - 104 one should be well off down to ET40 GeV cut-off.

Preliminary trigger rate analysis1:

1 Stefan Tapprogge

11

Upgrade scenarios and Forward detectors - CMS & TOTEM

4.11

• The Technical Proposal submitted in 1999• The Technical Design Report (TRD) to be completed by Fall 2002• Designed to co-exist with CMS and to run with large or intermediate * (1100m & 18m &...)• Aims at:

• Precision measurement of tot (tot ~ 1mb)• Elastic scattering down to -tmin ~ 10-3

• Inclusive (soft) diffractive scattering • Forward spectrometer:

• T1 & T2 for inelastics (3 < || < 7)Low-x 2002 Risto Orava

diffraction at lhc - experimental set-up risto orava university of helsinki and helsinki institute...

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