DETECTING DIFFRACTIVE
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DETECTING DIFFRACTIVE INTERACTIONS AT THE LHC. (1) Multivariate classification of diffractive and non-diffractive events at low lumi LHC. (2) Low mass central diffraction at LHCb. Risto Orava University of Helsinki, Helsinki Institute of Physics CERN.

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Low x Meeting ISCHIA ISLAND, ITALY September 8-13 2009

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Low x meeting ischia island italy september 8 13 2009

DETECTING DIFFRACTIVE

INTERACTIONS

AT THE LHC

(1) Multivariate

classification

of diffractive

and non-diffractive

events at low lumi

LHC.

(2) Low mass central

diffraction at LHCb.

Risto Orava

University of Helsinki,

Helsinki Institute of Physics

CERN

Low x Meeting ISCHIA ISLAND, ITALY September 8-13 2009


Low x meeting ischia island italy september 8 13 2009

  • The event classification studies by

  • The Helsinki Group members:

  • Mikael Kuusela, Jerry W. Lämsä, Eric Malmi,

  • Petteri Mehtälä and RO

  • of the University of Helsinki, the Helsinki Institute

  • of Physics, FI.

  • in Association with the Adaptive Informatics Research

  • Centre, Helsinki University of Technology, FI.


Low x meeting ischia island italy september 8 13 2009

SPACE-TIME STRUCTURE OF DIFFRACTIVE EVENTS

sTOTsEL + sSD + sDD + sCD + sND

HOW TO CLASSIFY INELASTIC LHC EVENTS AS SD, DD, CD or ND

IN AN EXPERIMENT?


Low x meeting ischia island italy september 8 13 2009

PREDICTIONS FOR THE DIFFRACTIVE CROSS SECTIONS

VARY...

sCD anywhere between a few mb’s to a few mb’s.

LOW MASS DIFFRACTION IS NOT UNDERSTOOD – WINDOW OF

OPPORTUNITY FOR EARLY LHC.


Low x meeting ischia island italy september 8 13 2009

FORWARD DETECTORS (1):

THE ROMAN POTS AND ZDC

ZDC detects neutrals at 0o

IN THIS ANALYSIS,THE ROMAN POTS ARE NOT USED IN CLASSIFYING THE LHC EVENTS.


Low x meeting ischia island italy september 8 13 2009

(2) T1, T2 SPECTROMETERS, AND

CASTOR

T1 and T2 detect particle flows

CASTOR

detects energy flows


Low x meeting ischia island italy september 8 13 2009

(3) PROPOSED FORWARD SHOWER

COUNTERS

FSCs DETECT

INTERACTIONS

IN THE BEAM

PIPE

60 to 140 meters

IP


Low x meeting ischia island italy september 8 13 2009

ENERGIES MULTIPLICITIES

23 INPUTS FOR EVENT CLASSIFICATION


Low x meeting ischia island italy september 8 13 2009

INPUT INFORMATION FOR EVENT

CLASSIFICATION

AIM AT A PROBABILISTIC APPROACH: EACH EVENT TO BELONG TO EVERY ONE OF THE EVENT CLASSES WITH A WEIGHT  0.


Low x meeting ischia island italy september 8 13 2009

INPUT

FOR

EVENT

CLASSIFICATION

LEADING

PROTONS

ARE NOT USED


Low x meeting ischia island italy september 8 13 2009

NOTE: LUMINOSITIES OF THE ORDER OF 1030 cm-2s-1 ASSUMED

 NO PILE-UP


Low x meeting ischia island italy september 8 13 2009

MULTIVARIATE TECHNIQUES


Low x meeting ischia island italy september 8 13 2009

unitary function

tail

-*/aQbcaacb

Karva expression of a chromosome:

letters: members

of the terminal set

Translated into an

expression tree; read

from left to right.

Note: Some of the tail

section is not used!


Low x meeting ischia island italy september 8 13 2009

SOM ALGORITHM

CD

SD

SD

DD

ND


Low x meeting ischia island italy september 8 13 2009

THE 23 SOM MAP NODES


Low x meeting ischia island italy september 8 13 2009

EVENT CLASSIFICATION EFFICIENCIES

MethodEfficiency

GEP ordered binarization92.49

GEP one-against-all88.54

SVM ordered binarization94.21

SVM one-against-one94.38

NN ordered binarization94.54

NN 5 outputs94.42


Low x meeting ischia island italy september 8 13 2009

EVENT CLASSIFICATION PURITIES

MethodDDSDCDND

GEP ordered binarization96.7283.4593.1297.81

GEP one-against-all83.8582.7891.0197.18

SVM ordered binarization97.7584.4096.3799.97

SVM one-against-one97.6184.8996.6199.90

NN ordered binarization97.4485.1997.0499.92

NN 5 outputs97.7084.9696.6699.92


Low x meeting ischia island italy september 8 13 2009

CONCLUSIONS – PART 1


Low x meeting ischia island italy september 8 13 2009

CONCLUSIONS – PART 1...


Low x meeting ischia island italy september 8 13 2009

CENTRAL DIFFRACTION AT THE LHCb

LHCb IS IDEAL FOR DETECTING AND ANALYSING LOW MASS

CENTRAL DIFFRACTIVE PRODUCTION OF EXCLUSIVE p+p-/K+K-

STATES IN:

pp p + M + p

glueballs, hybrids, heavy quarkonia: c, b

p+p-/K+K- STATES AS SPIN-PARITY ANALYZERs.

HOW TO FACILITATE THIS?

Jerry W. Lämsä and RO


Low x meeting ischia island italy september 8 13 2009

LHCb


Low x meeting ischia island italy september 8 13 2009

THE PROPOSED LHCb FSC LAY-OUT

ADD FSCs AT 20 – 100 METERS ON BOTH SIDES OF IP8 – THE FSCs

DETECT SHOWERS FROM THE VERY FORWARD PARTICLES.


Low x meeting ischia island italy september 8 13 2009

TRIGGER FOR LOW CHARGED MULTIPLICITIES IN THE SPD, RESTRICT NO. OF CHARGED TRACKS IN VELO AND ABSENCE OF A SIGNAL IN FSCs

  • TO DETECT A LOW MULTIPLICITY DECAY, A SMALL NUMBER OF CHARGED TRACKS ARE REQUIRED TO STRIKE THE SCINTILLATOR PAD DETECTOR (SPD).

  • THE LHCb VErtex LOcator (VELO) IS REQUIRED TO HAVE NO CHARGED TRACKS (CENTRAL ANGLE VETO) WITHIN 10 – 170 deg.

  • SIMULATION USES A COMBINATION OF PHOJET+PYTHIA & GEANT.

  • ANGULAR ACCEPTANCE OF THE SPECTROMETER: < 250 mrad (vertical),

  • < 300 mrad (horizontal)

  • NOTE: IN LOW LUMINOSITY LHCb RUNS, ONLY A SINGLE INTERACTION

  • PER BX IS EXPECTED.


Low x meeting ischia island italy september 8 13 2009

p

p

p

p

p

p

p

p

p+

p+

K+

K+

p-

p

p

p-

K-

p

p

p

p

K-

p

p

PURITIES FOR EXCLUSIVE STATES

DM  20 MeV


Low x meeting ischia island italy september 8 13 2009

CENTRAL DIFFRACTION ACCEPTANCE


Low x meeting ischia island italy september 8 13 2009

CENTRAL DIFFRACTION PURITY


Low x meeting ischia island italy september 8 13 2009

CONCLUSIONS – PART 2

Feasibility studies of the exclusive diffractive processes for the LHCb

experiment have been carried out.

With a simple addition of Forward Shower Counters (FSCs), the experiment

is shown to be ideally suited for detailed QCD studies and searches for

exotic mesons states, such as glueballs, hybrids, and heavy quarkonia.


Low x meeting ischia island italy september 8 13 2009

SINGLE DIFFRACTION BACKGROUND

SD events that satisfy the SPD trigger requirement ~9%

with the FSC veto


Low x meeting ischia island italy september 8 13 2009

SINGLE DIFFRACTION BACKGROUND

The contributions from single diffractive events that produce a unique

p+p-/K+K- pair within the detector acceptance vs. mass of the pair.


Low x meeting ischia island italy september 8 13 2009

FSC EFFICIENCY vs. DIFFRACTIVE MASS


Low x meeting ischia island italy september 8 13 2009

NON-DIFFRACTIVE BACKGROUND


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