Small X and Diffraction 2003
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Small X and Diffraction 2003 at Fermilab 17-20.9.2003. The TOTEM Experiment. K . Österberg High Energy Physics Division, Department of Physical Sciences, University of Helsinki & Helsinki Institute of Physics on behalf of the TOTEM Collaboration http://totem.web.cern.ch/Totem/.

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K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Small X and Diffraction 2003

at Fermilab

17-20.9.2003

The TOTEM Experiment

K. Österberg

High Energy Physics Division, Department of Physical Sciences, University of Helsinki & Helsinki Institute of Physics

on behalf of the

TOTEM Collaboration

http://totem.web.cern.ch/Totem/


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Collaboration


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

The measurement of stot

  • Historical: CERN tradition (PS-ISR-SPS)

  • Dispersion relation (logs),   2.0

  • Current model predictions: 100-130 mb (at s = 14 TeV)

  • Aim of TOTEM: ~1% accuracy

  • Using the luminosity independent method

  • Absolute determination of luminosity

Optical Theorem:


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

  • To measure the total cross section with ~ 1% precision:

  • measure elastic rate to lowest possible t (t  10-3 GeV2) and extrapolate rate to t = 0 with a precision of < 0.5 %

  • measure total inelastic rate with a precision of < 1 %

  • Roman Pot detectors to measure leading protons - T1 and T2 detectors to measure inelastic events

~150m

~215m


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

vx(1100)

vx(1540)

vy(1540)

vy(1100)

Special LHC optics for the measurement of leading protons

  • Measuring elastic protons with t  10–3 GeV2  scattering angles of a few rad

  • At the IP : small beam divergence

  • [sq=(e / b*)1/2]  large b* (b* O(km))

  • At the detector stations:

  • y = Leff,yqy* + vy y*

  • x = Leff,xqx*+vx x*+Dx x

  • Optimal conditions:

  • parallel to point focusing planes (v = 0) 

  • unique position – scattering angle relation

  • large Leff scattered proton at sizeable

  • distance from the beam center (~ 1 mm)

  • lowest possible beam emittance (  1 m . rad)

  • Luminosity :  1028 cm-2 s-1

  • Two alternative optics (b*= 1100 m and 1540m) are under careful study:

  • - With b*= 1540 m parallel to point focusing planes in x and y simultaneously at ~220 m

High * optics: lattice functions


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

b* = 1100 m

Elastic scattering

acceptance

* = 1100 m

* = 1540 m

Large t (1-10 GeV2) elastic scattering will be measured using injection optics (* = 18 m)


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Elastic rate at t = 0: statistical and systematical uncertainties

L = 1028 cm-2 s-1

run time = 4 . 104 s

10 m detector position uncertainty

Total systematical uncertainty < 0.5 %

Systematical uncertainties: beam angular divergence and crossing angle, optical functions, beam position, detector position and resolution, pot alignment, effect of backgrounds (beam halo, double Pomeron exchange).


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

t acceptance and t resolution

50 % t acceptance vs detector position w.r.t. the beam center

uncertainty on t acceptance vs uncertainty of detector position

(%)

t=0.004 GeV2 A=44%

t=0.01 GeV2 A=67%

 = 1100 m

t=0.004 GeV2 A=64%

t=0.01 GeV2 A=78%

= 1550 m

 (t)/t (1 arm) vs detector resolution

  • smallest possible t measured when distance between sensitive edge of detector and bottom of pot is as short as possible

  • detector resolution of  20 m sufficient

  • detector position w.r.t. the beam center should be known to better than 20 m

total

without beam

divergence


Leading proton detectors

CMS Hybrid

~3cm

Leading proton detectors

  • High and stable efficiency near the edge facing the beam, edge sharpness < 10 m  try to do detectors with thinner guard rings than present LHC technology  0.5 mm

  • Detector size is  3  4 cm2

  • Spatial resolution  20 m

  • Moderate radiation tolerance ( 1014 1 MeV neutron / cm2 equivalent)

  • Currently four different silicon based options are actively pursued:

  • cut planar strip detectors operated at cryogenic temperatures (“cold silicon”)

  • development of cut planar strip detectors (for operation at higher temperatures)

  • 3D-detectors with active edges

  • planar strip detectors with active edges


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

p+

C

p+

D

B

A

B

A

n+

n+

Cut edge reconstruction(2002)

Cold silicon

Planar strip detectors without guards rings operated at cryogenic temperatures (~ 130 K).

Efficiency

  • low bias voltage

  • radiation hard

Z. Li et al, "Electrical and TCT characterization of edgeless Si detector diced with different methods", IEEE NSS Proc., San Diego, Nov. 2001

Edge at: 0+20micron

Development of planar technology

cut edge

cut edge

Idea: additional n+ or p+ ring to prevent current C

Goal: increase the operation temperature


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

3D detectors with active edges

Brunel, Hawaii, Stanford

  • CERN Courier, Vol 43, Number 1, Jan 2003

  • fast charge collection

  • low bias voltage

  • radiation hard

signal a.u.

edge sensitivity 5-20 m

position [mm]

Planar strip detectors with active edges

Brunel, Hawaii, Stanford

TRADITIONAL PLANAR DETECTOR

+ DEEP ETCHED EDGE FILLED

WITH POLYSILICON

E-field

p + Al

signal a.u.

n + Al

position [mm]

edge sensitivity 20 m

n + Al


Design of a roman pot

Design of a Roman Pot

first prototype ready by end 2003

  • Mechanical design of a thin window

  • Secondary vacuum: outgassing and RF shielding; radiation hardness

  • Integration of detectors inside the pot - mounting, cooling, routing

  • High mechanical precision ( 20 m) and reproducibility

QRL (LHC Cryogenic Line)

Roman Pot station design

and tunnel integration

4m


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Microstation – an option to Roman Pots

  • A compact and light but still a robust and reliable system

  • Integrated with the beam vacuum chamber

  • Geometry and materials compatible with machine requirements

  • Detector movement with m accuracy

Emergency actuator

Development in

cooperation with LHC

machine groups

Inch worm motor

6cm

Space for cables and cooling link

Inner tube for rf fitting

Detector

Space for encoder

Note: A secondary vacuum is an option.

M. Ryynänen, R. Orava. /Helsinki group


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Forward inelastic detectors T1 & T2

  • T1: 5 planes of CSC chambers/side

  • coverage: 3.1 <  < 4.7 & full azimuthal

  • spatial resolution better than 0.5 mm

  • T2: 5 planes of silicon detectors/side

  • coverage: 5.3 <  < 6.7 & full azimuthal

  • spatial resolution better than 20 m

IP

7.5 m

3.0 m

T1 detector

HF

Castor

 IP

13.6 m

0.4 m

T2 detector


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

TOTEM+CMS+

CASTOR

Measurement of the inelastic rate

  • T1, T2 and the forward leading proton detectors allow fully inclusive trigger:

  • DD, MB -- double arm inelastic trigger

  • SD -- single arm inelastic + single arm leading proton

  • Elastics, DPE -- double arm leading proton trigger

  • Vertex reconstruction necessary for disentangling beam-beam events from background

Event loss < 2%

Uncertainty < 1%

Diffraction

Combining TOTEM and CMS makes a large acceptance detector.

90 % of all diffractive protons detected (high )

Diffractive measurements at LHC energies important for the understanding of cosmic ray events.


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

p1

p’1

p

M2=x1x2s

p

p2

p’2

CMS/TOTEM collaboration for high luminosity (* = 0.5 m)diffraction

150 m

215 m

308 m

420 m

338 m

e.g. Double Pomeron Exchange (DPE)

M (GeV)

x1= x2

x=Dp/p proton momentum loss

Trigger via Roman pots x > 2.5%

Trigger via rapidity gap/central systemx < 2.5%


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Exclusive DPE – proton acceptance and mass resolution (* = 0.5 m)

Event fraction with both protons within acceptance vs central system mass

Mass resolution of central system

1

pp p + X + p

0.03

pp p + X + p

all

all

215 m

 (mass)/mass

308 m

0.02

420 m

accepted fraction

0.01

0

100

300

500

700

mass of system X (GeV)

0.5

0.04

all

308 m

420 m

0.03

 (mass)/mass

0.02

0.01

0

0

140

60

100

180

60

100

140

180

mass of system X (GeV)

mass of system X (GeV)

At 120 GeV mass for central system: 50 % proton efficiency and 2 % resolution


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Running scenario

  • Total Cross Section and Elastic Scattering

  • Several 1 day runs with high b*

  • Several 1 day runs with b* = 18 m for large-t elastic scattering

  • Diffraction

  • Runs with CMS with high b* for L =1028cm-2 s-1

  • Runs with CMS with b* = 0.5 m for L < 1033cm-2 s-1

Plans

  • Test of silicon detectors (2003-04)

  • Roman pot prototype by end 2003

  • Technical Design Report by end 2003

  • CMS/TOTEM collaboration for high luminosity diffraction


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Backup Slides


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Elastic scattering

Coplanarity test, background rejection: azimuthal angle resolution

Detector resolution = 20 mm


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Total TOTEM/CMS acceptance (* = 1540 m)

RPs


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

log(-t) (GeV2)

Elastic and total TOTEM/CMS acceptance (* = 18 m)

b = 18 m

b = 1540 m

RPs

RPs


Radiation fluence in the rp silicon detectors n mokhov i rakhno fermilab conf 03 086

Radiation fluence in the RP silicon detectors(N.Mokhov,I. Rakhno,Fermilab-Conf-03/086)

Maximum fluence (1014 cm-2) for charged hadrons

(E>100 KeV , L= 1033 cm-2 s-1, t=107s):

RP4 (215 m)  Vertical: 0.58, Horizontal: 6.7

Dose (104 Gy/yr)

RP4 (215 m)  Vertical: 0.37 (max: 1.9), Horizontal:1.2 (max:55)

Main source of background: pp collisions

Tails from collimators and beam-gas scattering ~ 0.1-1%

Radiation level manageable


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Forward inelastic detector T1

RAILS ARE ASSEMBLED ON A TRUSS STRUCTURE, TO WITHSTAND THE FLEXURAL LOAD

THE TRUSS IS COMPLETELY RESTRAINED ON THE OUTERMOST SPACER RING

PUSH/PULL RODS AT THE END TIE THE 2 TRUSSES AND LIMITS THE TORSION

BASIC SOLUTION: STEEL MADE, ONE TRUSS WEIGHS ROUGHLY 120 Kg

PUSH ROD: COULD BE MADE OF ALUMINIUM OR FIBERGLASS (BETTER PARTICLE TRANSPARENCY) AND/OR ARC-SHAPED

PUSH/PULL RODS

TRUSS

(In agreement with CMS)


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Forward inelastic detector T2

Lightweight Structure

Space for services

 470 mm

Bellow

Weight estimation:

~30 Kg

Thermal Insulation

400 mm


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Trigger and event rates

Event rates at L = 1028 cm-2 s-1 :

Elastic (~ 30 mb)~ 300 Hz

Inelastic (~ 80 mb) 100 Hz (suitably prescaled)

Running time per high-b run ~ 2·104 s (10 hours, 50% efficiency):

~ 6 ·106 elastic events

~ 2 · 106 inelastic events

  • Statistics (large-t elastic) :

    • t ~ 0.5 GeV2 :~ 200 evts/bin(0.02 GeV2 bins)

    • t ~1.5 GeV2 :~ 80 evts/bin(0.05 GeV2 bins)

b* = 18 m 2800 bunches

L ~ 1032 cm-2 s-1 for 2·104 s (10 hours, 50% efficiency)

  • t ~ 6 GeV2 :~ 25 evts/bin(0.1 GeV2 bins)


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

x=0.06

x=0.01

x<10-3

Diffraction at high 

-t=10-2

-t=10-1

log(-t) (GeV2)

90% of all diffractive protons

are seen in the Roman Pots


Dispersion function for lhc low optics cms ir

Dispersion function for LHC low * optics (CMS IR)

horizontal offset x=Dx

For a diffractive proton with a 5  10-3 momentum loss to give an offset in the horizontal plane of (at least) 5 mm  dispersion in x  1 m  need proton detectors located > 400 m from interaction point.

Dx

x

y

Optical function  in x andy(m)

Dispersion in horizontal plane(m)

CMS


Acceptance vs mass of central system

Acceptance vs mass of central system

pp p + X + p

  • Combined acceptance of

  • all locations (dotted)

  • 420 m + 215 m (dashed)

  • 215 m alone (solid)

  • 420 m alone (dash-dotted)

  • 308/338 m location brings 10-15 % more acceptance

1

fraction of events with both protons within acceptence

0

400

800

0

0

mass of system X (GeV)


K sterberg high energy physics division department of physical sciences university of helsinki helsinki institute o

Trigger timing of RP4 at 215 m


Case study l1 trigger for diffractive higgs based on decay products

Case study: L1 trigger for diffractive Higgs based on decay products

  • Start from diffractive Higgs sample with auxiliary conditions

  • Both protons within acceptance of leading proton detectors

  • Both b-jets within Silicon Tracker acceptance (||<2.5) since b-tag will anyhow have to be required to reduce gg background.

Use 2 most energetic jets in ||<3. diffractive Higgs characteristics: back-to-back in azimuthal, small forward ET (3<||<5) and ET sum  MH.

diff. Higgs

diff. Higgs

forward ET (3<||<5)

azimuthal angle correlation

L = 1033 cm-2 s-1

MH = 120 GeV

inelastic

inelastic


Case study l1 trigger for diffractive higgs based on decay products1

Case study: L1 trigger for diffractive Higgs based on decay products

Combining 2 jet azimuthal angle sum, ET sum,  sum and difference + forward ET

0

diffractive Higgs

inelastic bkg

-0.7

log10(efficiency)

Preliminary !!

MH = 120 GeV

log10(Higgs efficiency)

-0.8

-2

L = 1033 cm-2 s-1

-0.9

-1

-4

3

4

2

cut on combined likelihood

log10(background rate(Hz))

If allowed additional L1 rate from a diffractive Higgs trigger is 250 Hz    12 % (includes L1 trigger efficiency, protons and b jets within resp. detector acceptance)

In addition signal is affected by Br (H  bb), tagging efficiency of b-jets and HLT efficiency.


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